June 15, 2015 • 39 mins
It's time for Electronics 101. What are the basic components of electronic circuits and what do they do? Jonathan explains.
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Episode Transcript
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Speaker 1 (00:04):
Get in touch with technology with text stuff from dot com.
Hey there, and welcome to text stuff. I'm Jonathan Strickland,
and today I wanted to address some listener mail and
and do a full episode based upon a request. This
(00:24):
comes from Chris via email Now. Chris wrote an incredible email,
very long, lots of different stuff in it and lots
of different suggestions, one of which was about the topic
will be covering today. So here's that section of the email,
so don't don't be alarmed. I'm going in medias race.
This is the middle of the email here or really
(00:45):
the end. Lastly, I was hoping in the future to
see topics covered like how electronics work, transistors, capacitors, chips, etcetera.
I worked at radio Shack for five years and got
really interested in electronic components, but found them pretty confusing.
That is perfectly understandable. I still have to look up
the various components and remind myself what each one does
(01:07):
because I don't tend to work with electronic circuits that frequently,
and I know in general what needs to happen, but
sometimes I forget the specifics because there's a lot of
stuff there, and if you aren't familiar. If you're not
always working in that world, it can very easily slip
away from you. And we are talking about lots of
(01:27):
different components that you measure using different units, And after
a while you just start to you know, if you again,
if you're not just naturally inclined to this kind of stuff,
you start to pull your hair out. Except in my case,
that's already been done for me, so I just kind
of rubbed my head. So let's start with the basics.
And I know this is going to sound incredibly basic,
(01:48):
but we have to build a foundation before we can
start talking about the components. So electronics are all about
leveraging electricity. Not a big surprise, you're you're leveraging electricity
in order to do something to accomplish something like a
radio is meant to receive and amplify radio signals and
and convert them into acoustic signal so that you can
(02:10):
actually hear them. That that's a simple example. A flashlight
is meant to channel electricity to end up powering a
light bulb, which is essentially a resistor. We will talk
about those that heats up. We're talking about a basic
incandescent light bulb here, Um and gives off light as
(02:30):
a result. That's your basic use of that kind of electronics.
So we're gonna talk about how electronics control electricity. These
basic components are all used to do that so that
you can accomplish whatever the goal of your electronic device is. Now,
most electronic devices have lots and lots of different components
(02:52):
to them, sometimes worked in various configurations, whether they're in
series or in parallel. I'm not going to get into
all all of that because that's beyond what I really
wanted to focus on in this episode. Instead, in this episode,
I want to talk about the very basic components and
what they are intended to do. These are the things
(03:14):
that make up the circuits that you would see in
physical circuitry. So if you ever have, uh, you know,
an old electronic device and you were to take it
apart and you saw all these little weird do dads
on a circuit board, I'm gonna tell you what those
do dads do. Dad. Alright, So first we describe an
(03:35):
electronics materials is having electrons that fall into certain energy
bands or electronic bands. Now, the two important ones that
to talk about are the valence band and the conduction band.
Electrons and the conduction band are able to move freely
through the material in question, assuming the conduction band isn't
totally full. You can think of it kind of like
a think of it like a nightclub. It's a nightclub
(03:59):
that's maybe you know, full, so you can still move
through it freely. Now that nightclubs packed, you're not going anywhere,
so there has to be you know, almost but not
quite full for you to be able to move around.
That's the conduction band. That's the basics of electrical conductivity. UH.
Whereas the valance band is kind of this um this
(04:21):
this basic energy level, and there is a gap between
the valence band and the conduction band. UH. It is
called the band gap. And depending upon the material, that
band gap will be of a certain size, and in
some cases the gap is insurmountable. You cannot get electrons
from the valence band into the conductance band, and you
(04:41):
cannot get them to flow, at least not under normal
operating circumstances. So in that sense, think of you've got
a like a holding room before you can get into
the nightclub, and the the doorway going into the nightclub
has got a big old bouncer and that a goal
bouncers not letting anyone through. That's your band gap. You
(05:04):
cannot there's no one even collectively all of you working together,
you're not gonna be able to budge that bouncer. That
would be as if you were in a non conducting
material and I'll get into more of that later. Whereas
if you're in a room where there's a wide open
door and you're allowed to go through as long as
someone else is coming in, that would mean that you
(05:26):
could flow through properly. You've got you got electrical electrical
conductivity going on there, and I'll talk more about that
in a second. I realized this analogy isn't perfect, but
I'm just trying to simplify things for those who haven't
really taken this kind of class in physics. So a
large gap would represent a great deal of energy needed
(05:47):
to move electrons from the valence band to the conductance band,
and sometimes that gap is so large as to be
impossible to cross again under normal operating conditions. So let's
look at the basic materials that we talk about in electronics, conductors, insulators,
(06:08):
and semiconductors. Pretty simple to understand. Conductors have high electrical conductivity.
That means they facilitate the flow of electrons. Uh. They
have a nearly full but not completely full conduction band.
Electrons can move freely through this material in response to
an electric field applied to that material. So you apply
(06:30):
an electrical field to this material, it will then allow
electrons to flow through freely. This is the stuff that
moves electrons from point A to point B. You apply
a voltage across it, you get electrons to flow. That's current,
Although technically current flows from positive to negative as opposed
to the flow of electrons, which is from negative to positive.
(06:51):
We can thank lots of early UH thinkers for that confusion.
So current flow and electron flow are in opposite to actions.
Thank you, Benjamin Franklin. Uh. Alright, So then you've got insulators.
These do not have electrons within the conduction band or
they have a full conduction band, so again no room
(07:11):
for electrons to move around, so there are no free electrons.
They impede the flow of electrons through that material, and
most solids fall into this category. Metals are UH an exception,
but most solids are insulators. So at normal operating parameters,
you wouldn't be able to apply a strong enough electric
field to make them conduct electricity. So you could apply
(07:35):
an electric field to these things, but it wouldn't be
able to jump that gap between the valence band and
the conductance band, so it would just stop. You wouldn't
have any electrical flow through that at all. So we
use insulators for things like insulation on wires where we
wrapped the wires in that to help prevent leakage or interference, because,
(07:58):
as we've talked about many times on this show, the
flow of electricity is also very closely related to magnetism
and vice versa. So you have to be able to
limit interference between different wires if you don't want there
to be that interaction obviously, otherwise you can end up
(08:19):
causing shorts, which is when you have an unintended connection
between two different elements of a circuit and it allows
electricity to pass from one to the other, almost like
you think of it like a short cut, you know,
when we say an electrical short and it means that
the device itself will not work properly because the electricity
is not flowing through the pathway you had intended it
(08:40):
to go in. All right, then we've got semi conductors,
and we'll talk more about them a little bit later,
but in general, semi conductors have an almost empty conduction
band and an almost full valence band, and the band
gap is relatively narrow. So if you don't apply a
strong enough electric field at as an insulator, but when
(09:01):
you apply the right amount of energy and electric field,
it will allow electrons jump from the valance band to
the conductor band and move freely within the material. You
do this by doping the material, which is when you
insert impurities into the semiconductor on purpose. Doping a semiconductor,
which is all about introducing impurities specifically at at predetermined levels,
(09:26):
will determine the energy levels required to do this, and
that's the basis for slid state electronics. We'll get into
more about semiconductors towards the end of this. And we
also have to remember voltage and current, something that I
always have trouble remembering. So voltage is a lot like
water pressure, all right. That's that's the the amount of
(09:49):
electrical pressure being applied, and the higher the voltage, the
more electrons want to move from the concentration of electrons
to the or positive side. Now, the actual flow of
electricity is the current, so they are related but not
the same thing. So voltage and current, and then you
(10:10):
multiply those two dependent together and you get the power.
So voltage times current equals power. Alright, So those are
your basics. Now we're gonna go through and talk about
the very individual components and what they do. So first
we have resistors. Resistor does pretty much what it sounds
like it does. It resists but does not halt the
(10:32):
flow of electricity. I'm gonna talk a lot about electricity
in terms of water because it is a useful analogy,
and it's also very common to talk about the similarities
between electricity flowing and water flowing when you're discussing these components.
So let's say that you have two different pipes. You've
got a brand spanking new pipe. It's shiny and beautiful
(10:56):
and free from any any irregularities, and it allows water
to flow through with a minimum of resistance. That water
is just flowing right through easily. You've got a second, old,
gnarly pipe, and this one's got calcium build up in it.
They're all these bumps and stuff on the inside. So
water actually encounters resistance friction, if you will, as it's
(11:18):
flowing through, and it does not flow through as easily.
Resistors are like that old gnarly pipe, and they are
invented on purpose for specific reasons. So why would you
want to have an electronic component that actually slows down
or impedes the flow of electricity for some reason. Well,
(11:40):
sometimes you have to limit the amount of electricity that
can flow through part of a circuit within a given
amount of time, sort of like how a faucet going
back to water, how fauce it can limit how much
water can flow through your water pipes into your sink.
So you wouldn't want just an on off switch for
the water coming into your home. That water is at
(12:00):
a much higher pressure, you know, it's it's a higher
pressure to deliver the water to your house. And if
all you had wasn't on off switch and you flipped it,
you would have water blasting through the pipe according to
the amount of pressure that was built up behind it.
That'd be a little bit nerving, especially if you just
wanted to have a nice frosty glass water. So you
(12:21):
want to have some sort of limiter on that to
control the amount of water that's or the pressure of
the water that's coming in. So resistors reduced the amount
of voltage placed on other electronic components within a circuit
by restricting the amount of current that can flow through
the resistor. The reason why this is important is that
(12:41):
we cannot create a battery for every single type of
electronic device that's out there. It's not practical. So batteries,
different batteries, Different types of batteries have different voltages. So
you could, in theory, develop a battery specifically for a
(13:03):
particular type of electronic device that would not require resistors
because the battery is providing exactly the voltage needed for
whatever electronic components are in net. But it's not practical
to do that for everything. We want standardized batteries, and
then we use things like resistors to help control the
voltage in those electronic components so that the right amount
(13:26):
of voltage is applied to those specific parts of the
electronic circuit, rather than having to have a billion different
types of batteries. That would not be practical. So there
are many different types of resistors designed to work on
specific amounts of electrical power. Now, some have changeable resistor
values dependent upon the amount of voltage placed across them.
(13:49):
They're called nonlinear or voltage dependent resistors. Resistor values can
also change when the temperature of the resistor changes UH.
Different types of resistors do this. Some can also be
mechanically adjusted. So it all depends upon what you need
the resistor for and why what you needed to do.
That's what would determine which type of resistor you would use.
(14:13):
The unit of measurement for a resistor is the ohm
oh h M. Resistor values are ten percent apart from
each other, and resistors are color coded with bands of
color or rings of color. So the first ring represents
the first digit of the resistors value. So what you
would do is you would look at the first ring,
whatever color it was, you would cross reference that with
(14:35):
the with a color UH index, and it would tell
you what the value of the resistor is for the
first digit. The second ring tells you the value of
the second digit. So then you've got the two UH
the two digits that are involved. The third tells you
the power of ten to multiply by, so it might
be ten thousand, and then you would multiply. Let's say
(14:58):
that your first two digits are a twenty two and
a seven, and you would multiply that by ten thousand.
You have twenty seven thousand poems there, and the fourth
ring would tell you the tolerance of the resistor plus
or minus whatever percentage. Uh So, the physical size of
the resistor and the amount of power it can handle
tends to be proportional. So in other words, the larger
(15:19):
the resistor, the more power it can handle. In general.
So those are resistors covers that basic component. Now let's
move on to capacitors. Alright. So capacitors are similar to
batteries and that it's a means of storing electrical energy,
but unlike batteries, instead of creating an a uh, electrical
(15:43):
flow through a chemical reaction that is steady the entire
time it is designed to release a it's it's entire
stored electrical charge all at once. So let's say they've
got two leads of a capacitor. You have a difference
in voltage across these two leads. That's when a capacitor
(16:04):
is charged. So one lead has a greater build up
of electrons than the other lead does. Uh. Now, if
you were to connect the leads together, you would short them.
You would have a discharge of that capacitor and the
voltage would equalize across the two, so you get a
release of a quick burst of electricity. So capacitors can
(16:25):
pass alternating current freely. A C current will just pass
through a capacitor as if it were not really there.
Direct current, however, will charge a capacitor. It will have
that build up of electrons on one side, while the
other side doesn't get that build up of electrons, and
then you have that difference in voltage. Alternating current just
(16:45):
will pass back and forth through it without any problems.
So capacitors contain the same fundamental parts. You have at
least two conductive plates separated by a non conductive material.
That's the dilector. The amount of charge held by capacitor
is measured in units called faret's. But a faret is
(17:06):
a large amount of capacitance, so large that you don't
really ever talk about a ferret. Instead we end up
talking about micro farets, which are about a well, which
are one million of a ferret, so much smaller. Faret,
by the way, not ferret, two different things. Nice Mormot
(17:26):
capacitance is dependent upon surface area, so it's directly proportional
to the surface area of those leads. Those those capacity plates. Um.
It is indirectly proportional to the distance between the plates.
So the greater the distance between the plates, the lower
the capacitance. Uh. It's also uh dependent upon the dielectric
(17:49):
constant of the insulating material. And they are used for
things that need a quick release of electricity rather than
a steady flow. So, for example, a tradition all flash
on a camera. So you've got an old camera and
you've got the the the flash, Uh, you know it
bursts in this quick burst of light. Well, it needs
(18:09):
that quick It needs access to a quick burst of
electricity in order to do that, and that's what capacitors
are good for. And it takes some time for the
capacitors to build up the charge again so it can
do it another time. That's sort of you know, if
you're using the old ones, you hear that noise. It's
the the discharge and then charging of the capacitors that
(18:31):
require you to take a moment between taking pictures with
those old style camera flashes. Now obviously newer ones used
different a different approach, but you often have capacitors that
actually provide the electricity for those. Now, the voltage of
a capacitor cannot change instantly, it's important to remember, and
(18:53):
quick voltage changes in a capacitor produced large current changes.
Capacitor store energy in an electric field. Now, the reason
I mentioned all that is because we're now going to
talk about inductors, and inductors are kind of, um the
opposite of capacitors, or really maybe not even opposite is
(19:14):
the right way of saying it. In many ways that
they behave in opposite ways than capacitors do, but we'll
get to that. So basically, an inductor at its most
basic level is a coil of wires, so sometimes we
(19:34):
just call them coils and not inductors. Uh. They deal
with what is the electrical equivalent of momentum. So if
you're familiar with momentum, essentially this is that idea that
you get a you know, objects in motion tend to
stay in motion. So let's say you've got a large
mass moving at a particular velocity. It has a certain
(19:58):
amount of momentum, and you have to overcome that momentum
to slow down and stop that uh, that that mass.
So it's the same type of thing with inductors, except
we're talking about the electrical equivalent of momentum. We're talking
about the flow of electricity. So again going back to
the water analogy, Let's say that you've got a water hose,
(20:19):
a really long one, several hundred feet long, and you've
coiled it up so it's in a nice long coil
and it's filled with water. There are gallons of water
inside this hose, and the end of the hose is
tilted at such an angle so the water is not
just flowing right out. You put a plunger into the
other end and you start to press on the plunger
(20:41):
to push the water out. Now, all of that water
is not just going to simultaneously start to move together.
It actually is going to take some time for the
pressure you are applying to exert enough force to push
the water out to overcome the inertia within that coil
of water hose. And once you get that water coming
(21:02):
out at the speed at which it can come out
and you let go of the plunger, the plunger is
going to continue going down that tube because of inertia.
That's the same sort of thing with inductors, except instead
of water, we're talking about electricity. So coils of wire
will pass d C current but will block a C current.
So in other words, direct current can flow through an inductor,
(21:26):
but alternating current would be blocked because it cannot flow
the opposite way through the coil. So that makes it
the opposite of capacitors. Remember, capacitors would pass alternating current
that can flow straight through, but would block direct current.
Direct current would charge a capacitor a capacitor, but could
not just flow through the capacitor. In this case, direct
(21:47):
current can flow through an inductor, but a c alternating
current would be blocked. The standard unit of inductance is
the henry. I wish I could tell you why, but
I honestly don't know. I'm sure some of you out there,
you electricians, are very familiar with the reason why and
could tell me and feel free to I I honestly
(22:09):
do not off hand. No, the inductance of a coil
is indirectly proportional to the length of the coil, but
directly proportional to the cross sectional area of the wire, So,
in other words, the gauge of the wire is important here.
It's also proportional to the square of the number of
turns in the coil, and it's directly proportional to the
(22:30):
permeability of the core material. Now the core is whatever
this coil is wrapped around. Now it could be wrapped
around air, or it could be wrapped around something like iron,
which is incredibly effective. So those are that's what we're
talking about with the cords, whatever the wire or is
coiled around. So when current first starts flowing into the coil,
(22:51):
the coil wants to build up a magnetic field. We've
talked about this again and again that you start running
electricity through a coil of wire that's coiled around like
an iron core, like a nail, and you start to
you create an electro magnet. Well, once that field is built.
(23:11):
While while the magnetic field is building, the coil inhibits
the flow of current through the wire. But once the
field is built, current can flow normally through the wire.
So if you were to have an inductor hooked up
to a light bulb, let's say and you flip a
switch so that you know, technically in an electronics would
(23:32):
say that you close the switch, so you have created
a closed path so electrons can flow through. The electrons
would flow through the inductor, which would start to build
up a magnetic field. So at first you would get
the light bulb coming on, then it would start to
dim a bit because as that magnetic field is getting
built up the lightbulb, you know, the electricity would be
(23:52):
limited to the light bulb. It would actually act as
sort of resistor, and the light bulb would start to
get dimmer. But then eventually then that magnetic field would
get charged up as much as it can because it's
direct current, not alternating current, and you would reach a
level where it was stabilized. Current would flow fine. At
that point, you can actually turn off the switch, you
(24:17):
can open it. In other words, the magnetic field around
the coil would keep current flowing through the coil until
that magnetic field collapsed. So even though you turn the
switch to off, because you have an inductor, that lightbulb
would stay lit until the magnetic field and the inductor collapsed,
in which case it would stop inducing current to flow
(24:38):
through and the light bulb would go off. So the
experience you would have is turn the switch on, light
bulb comes on, light bulb starts to get dim, light
bulb gets bright again, You turn the switch off, lightbulb
stays lit for a while, and then turns off. That's
what it would look like to you, So pretty interesting
(24:59):
to me. Now. So, an inductor stores energy in its
magnetic field, and it tends to resist any change in
the amount of current flowing through it, thus making it
different from capacitors. Because capacitors store things an electric field,
inductor store things energy, not just things. Capacitor store energy
and electric fields, and inductor store energy and magnetic fields.
(25:23):
And capacitors resist changes to voltage, whereas inductors resist changes
to current. So really interesting about that. So because of
this relationship between inductors and capacitors, these two different components
are sometimes referred together as dual components because they they
are opposites that complement one another. The current in an
(25:46):
inductor cannot change instantly the quick current changes produced the
large voltage, and inductors store their energy in those magnetic fields.
That's what sets them opposite of capacitors, because they are
all the opposite of those things. And you might wonder
what are inductors used for. I mean, that lightbulb example
seems kind of crazy. Well, they're used for lots of stuff.
For example, if you've ever gone to uh, like traffic
(26:09):
lights that are that respond to the presence of vehicles.
Most of those are using inductors. So underneath the pavement
where you're driving on top of you know, there are
giant coils of wire, and when you stop your car
at a stoplight that has one of these systems, your
car starts to act as the core for that inductor loop.
(26:32):
You've got this massive amount of steel that's right there
that affects the inductance of the that cable. You have
a meter attached to the cable that measures the inductance.
So when it measures a change in inductance, that meter
knows there's a vehicle at that location and sends that
information to the control unit for the traffic system and
(26:55):
thus changes the traffic cycle so that you get a
green light faster. So if you're ever at one of
those intersections where the the light cycles depend heavily upon
whether or not there are cars present at the intersection,
that's generally speaking, what is happening. You've got these inductors.
The inductance changes, sends the message to the meter, or
(27:17):
rather the meter detects the inductor the change in inductance
and then sends that onto the traffic control system that
will then, at least in theory, get you on your
way a little faster. So that's inductors. Now let's take
a look at transformers, which are more than meets the eye.
(27:37):
So I'm not talking about autobots in Decepticons, as much
as I would love to do that, instead of talking
about the basic electronic component. So let's say you've got
a single core, like like that iron nail. Let's say
and you put multiple coils of wire over this same
iron core, and then you force a DC current through
(27:59):
one of those coils of wire, not all of them,
just one. Now, as that current charges, it will induce
current to flow through the other coils wrapped around that
same core, and constantly changing the voltage of that primary coil.
The one that you've got attached to some sort of
voltage generator will cause currents that change in a similar
(28:20):
fashion in the other coils. Now, if the other coils
have more loops than the primary coil, the voltage will
be greater, but the current will be lower. I'll explain
that in the second. So let's say we've got we'll
make it really simple. We'll just do two coils. Let's
say we've got an iron core and we've got a
primary wire coiled around it ten times, and we have
(28:42):
a second wire coiled in the same direction around that
iron core, but it is coiled twenty times, and we
apply a varying voltage across the primary wire. The voltage
across the second wire will be twice as much because
there are twice as many coils, but the current will
be as much as that in the primary coil. And
(29:03):
that's because you have to conserve power. You cannot create
or destroy power. You have to conserve it. And power,
like I said earlier, is equal to voltage times current.
So if we double the voltage, but ultimately the power
in the secondary coil has to be the same as
the primary coil. The only way to address that is
to have the current. So that's you know, that's what happens.
(29:28):
So if the second coil is coiled in the same
direction as the primary, like I was saying before, the
voltage is in the same polarity as that of the
generator the primary coil. If the second coil is coiled
in the opposite direction of the primary coil, then the
voltage is in the opposite polarity from the primary coil.
(29:49):
Polarity is really important but also pretty complicated, So I'll
probably spend another episode to explain that concept because it's
really a bit much to go into right now. But anyway,
this is the basics for power transmission using alternating current.
It's the reason why we have alternating current distributing our
(30:11):
power instead of direct current. So, and that old Tesla
versus Edison argument, really i should say Westinghouse versus Edison argument,
where Edison was saying direct current was best and Westinghouse
was saying no alternating current was best. The things that
let alternating current win out over direct current, or that
(30:32):
using transformers you could boost the voltage to huge high
voltage numbers, which were great for power transmission. You could
transmit over vast distances using high voltage wires, and then
you would use other transformers on the opposite end to
step down the voltage until you reach the level that
(30:53):
was safe for homes, which in the United States is
two forty volts. Uh. Now, keep in mind that when
you're talking about transmiss voltages, it could be anywhere between
a hundred fifty five thousand to seven sixty thousand volts.
So we're talking huge differences here, and it's all because
you could use this basic element of electronics with these
(31:14):
transformers to step up or step down the voltage simply
by using different coils along a core, So that was
incredibly useful. You could end up transmitting power over great distances.
Direct current, however, is very different. It is most efficient
if it is close to whatever the load is on
the line. So the load is whatever the electricity is
(31:38):
meant to power. So in the case of homes, you
would want the power plant to be relatively close to
the homes that are receiving electricity. If you were using
direct current, um this is you know, it would be
incredibly useful to have direct current powering our homes because
most of the stuff we have relies on direct current.
(32:00):
It actually has to convert the alternating current that comes
to the house into direct current. You have these converters
that are part of the electronics that allow it to
do that. If you had direct current being uh supplied
directly to your house, you wouldn't need the conversion part
of those devices. However, you wouldn't be able to transmit
(32:20):
it over great distances like you can with alternating current.
So in case you're wondering about the power grades in
the United States, we I mentioned that you have those
those high voltage lines that are carrying between a HUDD
to s hred sixty thousand volts. When you get to
distribution levels, you step down that voltage to less than
(32:41):
ten thousand volts typically, and then you get to distribution
buses that have transformers that reduce it further to seven thousand,
two hundred volts or less. And then you have the
homes that are connected to a final transformer that step
it down again to the voltage of two volts or so.
So incredibly useful and here at how stuff works. Recently,
(33:04):
as of the recording of this podcast, we had a
lovely transformer fire right next to the building we work in,
which cut power to our part of the building for
some time. So if you've ever been near a transformer
when it's blown, it's a pretty spectacular thing. It's usually
lots of sparks in a really loud bang, and often
requires the work of dedicated personnel to repair. And it
(33:30):
does also typically mean that you have a loss of
power for at least a localized area. Pretty impressive when
it happens. Luckily, it doesn't happen all that frequently. The
electrical storms and areas of or times of great use
can make them more vulnerable. Now let's move on to
(33:51):
semiconductors and how they are used in electronics. So we've
got lots of different uses for semiconductors. I'm going to
talk about two specific ones. There are iodes. Diodes are
really useful. They allow current to flow in only one direction,
so it's like a one way channel or a valve.
So electricity flowing one way is fine, but it cannot
flow back the other way, and semiconductor doping allows for
(34:14):
this to happen. Remember I mentioned earlier. Doping is when
you have introduced impurities into the semiconductor material to give
it specific UH features. So there are two different types
that we're going to talk about. There's end type layers
of semiconductors, so you can think of that as an
excess of electrons. It has lots of negative electrons that
(34:36):
are just ready to flow out of there. And then
you have P type layers and these have electron holes
or at least you know, in other words, of the
capacity to take on electrons. So if you pair this together,
you get what's called a P N diode, which only
allows electricity to flow in one direction. It can Electrons
(34:57):
can come through UH and flow to the holes, but
they can't go the other way, so very useful and
electronic components where you need to direct the flow of
electricity along a particular path and prevent it from coming
back through that pathway. Transistors are another type of semiconductor
(35:17):
that use a small amount of current to control a
large amount of current. So while a diode is p n,
transistors are either p n P or n p n,
and if you apply an electrical current to the center layer,
which is also known as the base, electrons will move
from the N type side to the P type side,
(35:39):
and that initial small current allows for much larger current
to flow through the material at that point. So transistors
act as switches or amplifiers incredibly useful. So when we
talk about transistors in solid state electronics, these are the
things that allow us to build logic circuits. And it's
because we can allow electrons to either flow or prevent
(36:03):
them from flowing. It's also why things like electron tunneling
can be such a problem. Electron tunneling is a quantum effect,
so you can think of an electron as not really
existing in a specific point in space at any given time,
but rather having the potential to exist in an area
of space at any point in time. So think of
(36:26):
it like a cloud where an electron could be, and
that cloud covers all the potential places the electron could be,
and there's different probability for different parts of the cloud.
If your transistor gates are so small, so narrow, so thin,
I guess I should say not narrow, that the cloud
of potential can overlap the transistor gate. That means there
(36:50):
is the possibility that at some point the electron could
exist on the other side of the transistor gate, even
if the gate never opened. And if there's a possibility,
that means sometimes it does appear on the other side
of the gate. We call it electron tunneling. It's not
really tunneling. It's just if there is the possibility that
could be on the other side, sometimes it is on
(37:12):
the other side, which means that you cannot actually control
the flow of electrons. In that case, it would mean
that your transistors would be ineffective in doing what they're
supposed to do. They wouldn't really be able to act
to switches reliably, and you would get errors in your computations.
It might work most of the time and then only
some of the time not work. But even then that's problematic,
(37:34):
which is one of the engineering challenges that transistor designers
and multi or rather microprocessor designers encounter all the time,
you know, finding new materials that are better at acting
as transistors switches, it's a big part of it. And
coming up with different architectures to really take advantage of
(37:54):
electron flow is another big part of it, alright. So
those are the basics, the basic electronic components that you
can talk about with, you know, if you're looking at
it from a very high level. Obviously there's tons of
other stuff that I didn't get into, and some of
it just requires you to pair up or otherwise put
(38:15):
into series or parallels some of the components I've mentioned
to to get whatever effects you want. But those are
the basics, so when you look at those different components,
you can remember that this is all about making sure
that the electrons are behaving in the way that makes
whatever it is you intend to do possible. I want
to thank Chris for sending that email in and asking
(38:38):
about this, because it was fun to cover this this
this topic again and to really kind of dive in
more deeply than I had before, and I want to
encourage you guys to write in and ask about other topics.
Whether it's a technology or a company or a person,
or maybe it's someone that you want to have on
the show, either as a guest host or someone for
(39:00):
me to interview. Any of that is fine. Please let
me know, or just feedback in general about the show.
I would love to hear more from you guys. Sent
me a message. The email address is tech Stuff at
how stuff works dot com, or drop me a line
on Facebook, Twitter, or Tumblr. The handle it all three
is tech Stuff H s W. And I'll talk to
you again really soon. For more on this and thousands
(39:28):
of other topics. Works dot com
Get in touch with technology with text stuff from dot com.
Hey there, and welcome to text stuff. I'm Jonathan Strickland,
and today I wanted to address some listener mail and
and do a full episode based upon a request. This
(00:24):
comes from Chris via email Now. Chris wrote an incredible email,
very long, lots of different stuff in it and lots
of different suggestions, one of which was about the topic
will be covering today. So here's that section of the email,
so don't don't be alarmed. I'm going in medias race.
This is the middle of the email here or really
(00:45):
the end. Lastly, I was hoping in the future to
see topics covered like how electronics work, transistors, capacitors, chips, etcetera.
I worked at radio Shack for five years and got
really interested in electronic components, but found them pretty confusing.
That is perfectly understandable. I still have to look up
the various components and remind myself what each one does
(01:07):
because I don't tend to work with electronic circuits that frequently,
and I know in general what needs to happen, but
sometimes I forget the specifics because there's a lot of
stuff there, and if you aren't familiar. If you're not
always working in that world, it can very easily slip
away from you. And we are talking about lots of
(01:27):
different components that you measure using different units, And after
a while you just start to you know, if you again,
if you're not just naturally inclined to this kind of stuff,
you start to pull your hair out. Except in my case,
that's already been done for me, so I just kind
of rubbed my head. So let's start with the basics.
And I know this is going to sound incredibly basic,
(01:48):
but we have to build a foundation before we can
start talking about the components. So electronics are all about
leveraging electricity. Not a big surprise, you're you're leveraging electricity
in order to do something to accomplish something like a
radio is meant to receive and amplify radio signals and
and convert them into acoustic signal so that you can
(02:10):
actually hear them. That that's a simple example. A flashlight
is meant to channel electricity to end up powering a
light bulb, which is essentially a resistor. We will talk
about those that heats up. We're talking about a basic
incandescent light bulb here, Um and gives off light as
(02:30):
a result. That's your basic use of that kind of electronics.
So we're gonna talk about how electronics control electricity. These
basic components are all used to do that so that
you can accomplish whatever the goal of your electronic device is. Now,
most electronic devices have lots and lots of different components
(02:52):
to them, sometimes worked in various configurations, whether they're in
series or in parallel. I'm not going to get into
all all of that because that's beyond what I really
wanted to focus on in this episode. Instead, in this episode,
I want to talk about the very basic components and
what they are intended to do. These are the things
(03:14):
that make up the circuits that you would see in
physical circuitry. So if you ever have, uh, you know,
an old electronic device and you were to take it
apart and you saw all these little weird do dads
on a circuit board, I'm gonna tell you what those
do dads do. Dad. Alright, So first we describe an
(03:35):
electronics materials is having electrons that fall into certain energy
bands or electronic bands. Now, the two important ones that
to talk about are the valence band and the conduction band.
Electrons and the conduction band are able to move freely
through the material in question, assuming the conduction band isn't
totally full. You can think of it kind of like
a think of it like a nightclub. It's a nightclub
(03:59):
that's maybe you know, full, so you can still move
through it freely. Now that nightclubs packed, you're not going anywhere,
so there has to be you know, almost but not
quite full for you to be able to move around.
That's the conduction band. That's the basics of electrical conductivity. UH.
Whereas the valance band is kind of this um this
(04:21):
this basic energy level, and there is a gap between
the valence band and the conduction band. UH. It is
called the band gap. And depending upon the material, that
band gap will be of a certain size, and in
some cases the gap is insurmountable. You cannot get electrons
from the valence band into the conductance band, and you
(04:41):
cannot get them to flow, at least not under normal
operating circumstances. So in that sense, think of you've got
a like a holding room before you can get into
the nightclub, and the the doorway going into the nightclub
has got a big old bouncer and that a goal
bouncers not letting anyone through. That's your band gap. You
(05:04):
cannot there's no one even collectively all of you working together,
you're not gonna be able to budge that bouncer. That
would be as if you were in a non conducting
material and I'll get into more of that later. Whereas
if you're in a room where there's a wide open
door and you're allowed to go through as long as
someone else is coming in, that would mean that you
(05:26):
could flow through properly. You've got you got electrical electrical
conductivity going on there, and I'll talk more about that
in a second. I realized this analogy isn't perfect, but
I'm just trying to simplify things for those who haven't
really taken this kind of class in physics. So a
large gap would represent a great deal of energy needed
(05:47):
to move electrons from the valence band to the conductance band,
and sometimes that gap is so large as to be
impossible to cross again under normal operating conditions. So let's
look at the basic materials that we talk about in electronics, conductors, insulators,
(06:08):
and semiconductors. Pretty simple to understand. Conductors have high electrical conductivity.
That means they facilitate the flow of electrons. Uh. They
have a nearly full but not completely full conduction band.
Electrons can move freely through this material in response to
an electric field applied to that material. So you apply
(06:30):
an electrical field to this material, it will then allow
electrons to flow through freely. This is the stuff that
moves electrons from point A to point B. You apply
a voltage across it, you get electrons to flow. That's current,
Although technically current flows from positive to negative as opposed
to the flow of electrons, which is from negative to positive.
(06:51):
We can thank lots of early UH thinkers for that confusion.
So current flow and electron flow are in opposite to actions.
Thank you, Benjamin Franklin. Uh. Alright, So then you've got insulators.
These do not have electrons within the conduction band or
they have a full conduction band, so again no room
(07:11):
for electrons to move around, so there are no free electrons.
They impede the flow of electrons through that material, and
most solids fall into this category. Metals are UH an exception,
but most solids are insulators. So at normal operating parameters,
you wouldn't be able to apply a strong enough electric
field to make them conduct electricity. So you could apply
(07:35):
an electric field to these things, but it wouldn't be
able to jump that gap between the valence band and
the conductance band, so it would just stop. You wouldn't
have any electrical flow through that at all. So we
use insulators for things like insulation on wires where we
wrapped the wires in that to help prevent leakage or interference, because,
(07:58):
as we've talked about many times on this show, the
flow of electricity is also very closely related to magnetism
and vice versa. So you have to be able to
limit interference between different wires if you don't want there
to be that interaction obviously, otherwise you can end up
(08:19):
causing shorts, which is when you have an unintended connection
between two different elements of a circuit and it allows
electricity to pass from one to the other, almost like
you think of it like a short cut, you know,
when we say an electrical short and it means that
the device itself will not work properly because the electricity
is not flowing through the pathway you had intended it
(08:40):
to go in. All right, then we've got semi conductors,
and we'll talk more about them a little bit later,
but in general, semi conductors have an almost empty conduction
band and an almost full valence band, and the band
gap is relatively narrow. So if you don't apply a
strong enough electric field at as an insulator, but when
(09:01):
you apply the right amount of energy and electric field,
it will allow electrons jump from the valance band to
the conductor band and move freely within the material. You
do this by doping the material, which is when you
insert impurities into the semiconductor on purpose. Doping a semiconductor,
which is all about introducing impurities specifically at at predetermined levels,
(09:26):
will determine the energy levels required to do this, and
that's the basis for slid state electronics. We'll get into
more about semiconductors towards the end of this. And we
also have to remember voltage and current, something that I
always have trouble remembering. So voltage is a lot like
water pressure, all right. That's that's the the amount of
(09:49):
electrical pressure being applied, and the higher the voltage, the
more electrons want to move from the concentration of electrons
to the or positive side. Now, the actual flow of
electricity is the current, so they are related but not
the same thing. So voltage and current, and then you
(10:10):
multiply those two dependent together and you get the power.
So voltage times current equals power. Alright, So those are
your basics. Now we're gonna go through and talk about
the very individual components and what they do. So first
we have resistors. Resistor does pretty much what it sounds
like it does. It resists but does not halt the
(10:32):
flow of electricity. I'm gonna talk a lot about electricity
in terms of water because it is a useful analogy,
and it's also very common to talk about the similarities
between electricity flowing and water flowing when you're discussing these components.
So let's say that you have two different pipes. You've
got a brand spanking new pipe. It's shiny and beautiful
(10:56):
and free from any any irregularities, and it allows water
to flow through with a minimum of resistance. That water
is just flowing right through easily. You've got a second, old,
gnarly pipe, and this one's got calcium build up in it.
They're all these bumps and stuff on the inside. So
water actually encounters resistance friction, if you will, as it's
(11:18):
flowing through, and it does not flow through as easily.
Resistors are like that old gnarly pipe, and they are
invented on purpose for specific reasons. So why would you
want to have an electronic component that actually slows down
or impedes the flow of electricity for some reason. Well,
(11:40):
sometimes you have to limit the amount of electricity that
can flow through part of a circuit within a given
amount of time, sort of like how a faucet going
back to water, how fauce it can limit how much
water can flow through your water pipes into your sink.
So you wouldn't want just an on off switch for
the water coming into your home. That water is at
(12:00):
a much higher pressure, you know, it's it's a higher
pressure to deliver the water to your house. And if
all you had wasn't on off switch and you flipped it,
you would have water blasting through the pipe according to
the amount of pressure that was built up behind it.
That'd be a little bit nerving, especially if you just
wanted to have a nice frosty glass water. So you
(12:21):
want to have some sort of limiter on that to
control the amount of water that's or the pressure of
the water that's coming in. So resistors reduced the amount
of voltage placed on other electronic components within a circuit
by restricting the amount of current that can flow through
the resistor. The reason why this is important is that
(12:41):
we cannot create a battery for every single type of
electronic device that's out there. It's not practical. So batteries,
different batteries, Different types of batteries have different voltages. So
you could, in theory, develop a battery specifically for a
(13:03):
particular type of electronic device that would not require resistors
because the battery is providing exactly the voltage needed for
whatever electronic components are in net. But it's not practical
to do that for everything. We want standardized batteries, and
then we use things like resistors to help control the
voltage in those electronic components so that the right amount
(13:26):
of voltage is applied to those specific parts of the
electronic circuit, rather than having to have a billion different
types of batteries. That would not be practical. So there
are many different types of resistors designed to work on
specific amounts of electrical power. Now, some have changeable resistor
values dependent upon the amount of voltage placed across them.
(13:49):
They're called nonlinear or voltage dependent resistors. Resistor values can
also change when the temperature of the resistor changes UH.
Different types of resistors do this. Some can also be
mechanically adjusted. So it all depends upon what you need
the resistor for and why what you needed to do.
That's what would determine which type of resistor you would use.
(14:13):
The unit of measurement for a resistor is the ohm
oh h M. Resistor values are ten percent apart from
each other, and resistors are color coded with bands of
color or rings of color. So the first ring represents
the first digit of the resistors value. So what you
would do is you would look at the first ring,
whatever color it was, you would cross reference that with
(14:35):
the with a color UH index, and it would tell
you what the value of the resistor is for the
first digit. The second ring tells you the value of
the second digit. So then you've got the two UH
the two digits that are involved. The third tells you
the power of ten to multiply by, so it might
be ten thousand, and then you would multiply. Let's say
(14:58):
that your first two digits are a twenty two and
a seven, and you would multiply that by ten thousand.
You have twenty seven thousand poems there, and the fourth
ring would tell you the tolerance of the resistor plus
or minus whatever percentage. Uh So, the physical size of
the resistor and the amount of power it can handle
tends to be proportional. So in other words, the larger
(15:19):
the resistor, the more power it can handle. In general.
So those are resistors covers that basic component. Now let's
move on to capacitors. Alright. So capacitors are similar to
batteries and that it's a means of storing electrical energy,
but unlike batteries, instead of creating an a uh, electrical
(15:43):
flow through a chemical reaction that is steady the entire
time it is designed to release a it's it's entire
stored electrical charge all at once. So let's say they've
got two leads of a capacitor. You have a difference
in voltage across these two leads. That's when a capacitor
(16:04):
is charged. So one lead has a greater build up
of electrons than the other lead does. Uh. Now, if
you were to connect the leads together, you would short them.
You would have a discharge of that capacitor and the
voltage would equalize across the two, so you get a
release of a quick burst of electricity. So capacitors can
(16:25):
pass alternating current freely. A C current will just pass
through a capacitor as if it were not really there.
Direct current, however, will charge a capacitor. It will have
that build up of electrons on one side, while the
other side doesn't get that build up of electrons, and
then you have that difference in voltage. Alternating current just
(16:45):
will pass back and forth through it without any problems.
So capacitors contain the same fundamental parts. You have at
least two conductive plates separated by a non conductive material.
That's the dilector. The amount of charge held by capacitor
is measured in units called faret's. But a faret is
(17:06):
a large amount of capacitance, so large that you don't
really ever talk about a ferret. Instead we end up
talking about micro farets, which are about a well, which
are one million of a ferret, so much smaller. Faret,
by the way, not ferret, two different things. Nice Mormot
(17:26):
capacitance is dependent upon surface area, so it's directly proportional
to the surface area of those leads. Those those capacity plates. Um.
It is indirectly proportional to the distance between the plates.
So the greater the distance between the plates, the lower
the capacitance. Uh. It's also uh dependent upon the dielectric
(17:49):
constant of the insulating material. And they are used for
things that need a quick release of electricity rather than
a steady flow. So, for example, a tradition all flash
on a camera. So you've got an old camera and
you've got the the the flash, Uh, you know it
bursts in this quick burst of light. Well, it needs
(18:09):
that quick It needs access to a quick burst of
electricity in order to do that, and that's what capacitors
are good for. And it takes some time for the
capacitors to build up the charge again so it can
do it another time. That's sort of you know, if
you're using the old ones, you hear that noise. It's
the the discharge and then charging of the capacitors that
(18:31):
require you to take a moment between taking pictures with
those old style camera flashes. Now obviously newer ones used
different a different approach, but you often have capacitors that
actually provide the electricity for those. Now, the voltage of
a capacitor cannot change instantly, it's important to remember, and
(18:53):
quick voltage changes in a capacitor produced large current changes.
Capacitor store energy in an electric field. Now, the reason
I mentioned all that is because we're now going to
talk about inductors, and inductors are kind of, um the
opposite of capacitors, or really maybe not even opposite is
(19:14):
the right way of saying it. In many ways that
they behave in opposite ways than capacitors do, but we'll
get to that. So basically, an inductor at its most
basic level is a coil of wires, so sometimes we
(19:34):
just call them coils and not inductors. Uh. They deal
with what is the electrical equivalent of momentum. So if
you're familiar with momentum, essentially this is that idea that
you get a you know, objects in motion tend to
stay in motion. So let's say you've got a large
mass moving at a particular velocity. It has a certain
(19:58):
amount of momentum, and you have to overcome that momentum
to slow down and stop that uh, that that mass.
So it's the same type of thing with inductors, except
we're talking about the electrical equivalent of momentum. We're talking
about the flow of electricity. So again going back to
the water analogy, Let's say that you've got a water hose,
(20:19):
a really long one, several hundred feet long, and you've
coiled it up so it's in a nice long coil
and it's filled with water. There are gallons of water
inside this hose, and the end of the hose is
tilted at such an angle so the water is not
just flowing right out. You put a plunger into the
other end and you start to press on the plunger
(20:41):
to push the water out. Now, all of that water
is not just going to simultaneously start to move together.
It actually is going to take some time for the
pressure you are applying to exert enough force to push
the water out to overcome the inertia within that coil
of water hose. And once you get that water coming
(21:02):
out at the speed at which it can come out
and you let go of the plunger, the plunger is
going to continue going down that tube because of inertia.
That's the same sort of thing with inductors, except instead
of water, we're talking about electricity. So coils of wire
will pass d C current but will block a C current.
So in other words, direct current can flow through an inductor,
(21:26):
but alternating current would be blocked because it cannot flow
the opposite way through the coil. So that makes it
the opposite of capacitors. Remember, capacitors would pass alternating current
that can flow straight through, but would block direct current.
Direct current would charge a capacitor a capacitor, but could
not just flow through the capacitor. In this case, direct
(21:47):
current can flow through an inductor, but a c alternating
current would be blocked. The standard unit of inductance is
the henry. I wish I could tell you why, but
I honestly don't know. I'm sure some of you out there,
you electricians, are very familiar with the reason why and
could tell me and feel free to I I honestly
(22:09):
do not off hand. No, the inductance of a coil
is indirectly proportional to the length of the coil, but
directly proportional to the cross sectional area of the wire, So,
in other words, the gauge of the wire is important here.
It's also proportional to the square of the number of
turns in the coil, and it's directly proportional to the
(22:30):
permeability of the core material. Now the core is whatever
this coil is wrapped around. Now it could be wrapped
around air, or it could be wrapped around something like iron,
which is incredibly effective. So those are that's what we're
talking about with the cords, whatever the wire or is
coiled around. So when current first starts flowing into the coil,
(22:51):
the coil wants to build up a magnetic field. We've
talked about this again and again that you start running
electricity through a coil of wire that's coiled around like
an iron core, like a nail, and you start to
you create an electro magnet. Well, once that field is built.
(23:11):
While while the magnetic field is building, the coil inhibits
the flow of current through the wire. But once the
field is built, current can flow normally through the wire.
So if you were to have an inductor hooked up
to a light bulb, let's say and you flip a
switch so that you know, technically in an electronics would
(23:32):
say that you close the switch, so you have created
a closed path so electrons can flow through. The electrons
would flow through the inductor, which would start to build
up a magnetic field. So at first you would get
the light bulb coming on, then it would start to
dim a bit because as that magnetic field is getting
built up the lightbulb, you know, the electricity would be
(23:52):
limited to the light bulb. It would actually act as
sort of resistor, and the light bulb would start to
get dimmer. But then eventually then that magnetic field would
get charged up as much as it can because it's
direct current, not alternating current, and you would reach a
level where it was stabilized. Current would flow fine. At
that point, you can actually turn off the switch, you
(24:17):
can open it. In other words, the magnetic field around
the coil would keep current flowing through the coil until
that magnetic field collapsed. So even though you turn the
switch to off, because you have an inductor, that lightbulb
would stay lit until the magnetic field and the inductor collapsed,
in which case it would stop inducing current to flow
(24:38):
through and the light bulb would go off. So the
experience you would have is turn the switch on, light
bulb comes on, light bulb starts to get dim, light
bulb gets bright again, You turn the switch off, lightbulb
stays lit for a while, and then turns off. That's
what it would look like to you, So pretty interesting
(24:59):
to me. Now. So, an inductor stores energy in its
magnetic field, and it tends to resist any change in
the amount of current flowing through it, thus making it
different from capacitors. Because capacitors store things an electric field,
inductor store things energy, not just things. Capacitor store energy
and electric fields, and inductor store energy and magnetic fields.
(25:23):
And capacitors resist changes to voltage, whereas inductors resist changes
to current. So really interesting about that. So because of
this relationship between inductors and capacitors, these two different components
are sometimes referred together as dual components because they they
are opposites that complement one another. The current in an
(25:46):
inductor cannot change instantly the quick current changes produced the
large voltage, and inductors store their energy in those magnetic fields.
That's what sets them opposite of capacitors, because they are
all the opposite of those things. And you might wonder
what are inductors used for. I mean, that lightbulb example
seems kind of crazy. Well, they're used for lots of stuff.
For example, if you've ever gone to uh, like traffic
(26:09):
lights that are that respond to the presence of vehicles.
Most of those are using inductors. So underneath the pavement
where you're driving on top of you know, there are
giant coils of wire, and when you stop your car
at a stoplight that has one of these systems, your
car starts to act as the core for that inductor loop.
(26:32):
You've got this massive amount of steel that's right there
that affects the inductance of the that cable. You have
a meter attached to the cable that measures the inductance.
So when it measures a change in inductance, that meter
knows there's a vehicle at that location and sends that
information to the control unit for the traffic system and
(26:55):
thus changes the traffic cycle so that you get a
green light faster. So if you're ever at one of
those intersections where the the light cycles depend heavily upon
whether or not there are cars present at the intersection,
that's generally speaking, what is happening. You've got these inductors.
The inductance changes, sends the message to the meter, or
(27:17):
rather the meter detects the inductor the change in inductance
and then sends that onto the traffic control system that
will then, at least in theory, get you on your
way a little faster. So that's inductors. Now let's take
a look at transformers, which are more than meets the eye.
(27:37):
So I'm not talking about autobots in Decepticons, as much
as I would love to do that, instead of talking
about the basic electronic component. So let's say you've got
a single core, like like that iron nail. Let's say
and you put multiple coils of wire over this same
iron core, and then you force a DC current through
(27:59):
one of those coils of wire, not all of them,
just one. Now, as that current charges, it will induce
current to flow through the other coils wrapped around that
same core, and constantly changing the voltage of that primary coil.
The one that you've got attached to some sort of
voltage generator will cause currents that change in a similar
(28:20):
fashion in the other coils. Now, if the other coils
have more loops than the primary coil, the voltage will
be greater, but the current will be lower. I'll explain
that in the second. So let's say we've got we'll
make it really simple. We'll just do two coils. Let's
say we've got an iron core and we've got a
primary wire coiled around it ten times, and we have
(28:42):
a second wire coiled in the same direction around that
iron core, but it is coiled twenty times, and we
apply a varying voltage across the primary wire. The voltage
across the second wire will be twice as much because
there are twice as many coils, but the current will
be as much as that in the primary coil. And
(29:03):
that's because you have to conserve power. You cannot create
or destroy power. You have to conserve it. And power,
like I said earlier, is equal to voltage times current.
So if we double the voltage, but ultimately the power
in the secondary coil has to be the same as
the primary coil. The only way to address that is
to have the current. So that's you know, that's what happens.
(29:28):
So if the second coil is coiled in the same
direction as the primary, like I was saying before, the
voltage is in the same polarity as that of the
generator the primary coil. If the second coil is coiled
in the opposite direction of the primary coil, then the
voltage is in the opposite polarity from the primary coil.
(29:49):
Polarity is really important but also pretty complicated, So I'll
probably spend another episode to explain that concept because it's
really a bit much to go into right now. But anyway,
this is the basics for power transmission using alternating current.
It's the reason why we have alternating current distributing our
(30:11):
power instead of direct current. So, and that old Tesla
versus Edison argument, really i should say Westinghouse versus Edison argument,
where Edison was saying direct current was best and Westinghouse
was saying no alternating current was best. The things that
let alternating current win out over direct current, or that
(30:32):
using transformers you could boost the voltage to huge high
voltage numbers, which were great for power transmission. You could
transmit over vast distances using high voltage wires, and then
you would use other transformers on the opposite end to
step down the voltage until you reach the level that
(30:53):
was safe for homes, which in the United States is
two forty volts. Uh. Now, keep in mind that when
you're talking about transmiss voltages, it could be anywhere between
a hundred fifty five thousand to seven sixty thousand volts.
So we're talking huge differences here, and it's all because
you could use this basic element of electronics with these
(31:14):
transformers to step up or step down the voltage simply
by using different coils along a core, So that was
incredibly useful. You could end up transmitting power over great distances.
Direct current, however, is very different. It is most efficient
if it is close to whatever the load is on
the line. So the load is whatever the electricity is
(31:38):
meant to power. So in the case of homes, you
would want the power plant to be relatively close to
the homes that are receiving electricity. If you were using
direct current, um this is you know, it would be
incredibly useful to have direct current powering our homes because
most of the stuff we have relies on direct current.
(32:00):
It actually has to convert the alternating current that comes
to the house into direct current. You have these converters
that are part of the electronics that allow it to
do that. If you had direct current being uh supplied
directly to your house, you wouldn't need the conversion part
of those devices. However, you wouldn't be able to transmit
(32:20):
it over great distances like you can with alternating current.
So in case you're wondering about the power grades in
the United States, we I mentioned that you have those
those high voltage lines that are carrying between a HUDD
to s hred sixty thousand volts. When you get to
distribution levels, you step down that voltage to less than
(32:41):
ten thousand volts typically, and then you get to distribution
buses that have transformers that reduce it further to seven thousand,
two hundred volts or less. And then you have the
homes that are connected to a final transformer that step
it down again to the voltage of two volts or so.
So incredibly useful and here at how stuff works. Recently,
(33:04):
as of the recording of this podcast, we had a
lovely transformer fire right next to the building we work in,
which cut power to our part of the building for
some time. So if you've ever been near a transformer
when it's blown, it's a pretty spectacular thing. It's usually
lots of sparks in a really loud bang, and often
requires the work of dedicated personnel to repair. And it
(33:30):
does also typically mean that you have a loss of
power for at least a localized area. Pretty impressive when
it happens. Luckily, it doesn't happen all that frequently. The
electrical storms and areas of or times of great use
can make them more vulnerable. Now let's move on to
(33:51):
semiconductors and how they are used in electronics. So we've
got lots of different uses for semiconductors. I'm going to
talk about two specific ones. There are iodes. Diodes are
really useful. They allow current to flow in only one direction,
so it's like a one way channel or a valve.
So electricity flowing one way is fine, but it cannot
flow back the other way, and semiconductor doping allows for
(34:14):
this to happen. Remember I mentioned earlier. Doping is when
you have introduced impurities into the semiconductor material to give
it specific UH features. So there are two different types
that we're going to talk about. There's end type layers
of semiconductors, so you can think of that as an
excess of electrons. It has lots of negative electrons that
(34:36):
are just ready to flow out of there. And then
you have P type layers and these have electron holes
or at least you know, in other words, of the
capacity to take on electrons. So if you pair this together,
you get what's called a P N diode, which only
allows electricity to flow in one direction. It can Electrons
(34:57):
can come through UH and flow to the holes, but
they can't go the other way, so very useful and
electronic components where you need to direct the flow of
electricity along a particular path and prevent it from coming
back through that pathway. Transistors are another type of semiconductor
(35:17):
that use a small amount of current to control a
large amount of current. So while a diode is p n,
transistors are either p n P or n p n,
and if you apply an electrical current to the center layer,
which is also known as the base, electrons will move
from the N type side to the P type side,
(35:39):
and that initial small current allows for much larger current
to flow through the material at that point. So transistors
act as switches or amplifiers incredibly useful. So when we
talk about transistors in solid state electronics, these are the
things that allow us to build logic circuits. And it's
because we can allow electrons to either flow or prevent
(36:03):
them from flowing. It's also why things like electron tunneling
can be such a problem. Electron tunneling is a quantum effect,
so you can think of an electron as not really
existing in a specific point in space at any given time,
but rather having the potential to exist in an area
of space at any point in time. So think of
(36:26):
it like a cloud where an electron could be, and
that cloud covers all the potential places the electron could be,
and there's different probability for different parts of the cloud.
If your transistor gates are so small, so narrow, so thin,
I guess I should say not narrow, that the cloud
of potential can overlap the transistor gate. That means there
(36:50):
is the possibility that at some point the electron could
exist on the other side of the transistor gate, even
if the gate never opened. And if there's a possibility,
that means sometimes it does appear on the other side
of the gate. We call it electron tunneling. It's not
really tunneling. It's just if there is the possibility that
could be on the other side, sometimes it is on
(37:12):
the other side, which means that you cannot actually control
the flow of electrons. In that case, it would mean
that your transistors would be ineffective in doing what they're
supposed to do. They wouldn't really be able to act
to switches reliably, and you would get errors in your computations.
It might work most of the time and then only
some of the time not work. But even then that's problematic,
(37:34):
which is one of the engineering challenges that transistor designers
and multi or rather microprocessor designers encounter all the time,
you know, finding new materials that are better at acting
as transistors switches, it's a big part of it. And
coming up with different architectures to really take advantage of
(37:54):
electron flow is another big part of it, alright. So
those are the basics, the basic electronic components that you
can talk about with, you know, if you're looking at
it from a very high level. Obviously there's tons of
other stuff that I didn't get into, and some of
it just requires you to pair up or otherwise put
(38:15):
into series or parallels some of the components I've mentioned
to to get whatever effects you want. But those are
the basics, so when you look at those different components,
you can remember that this is all about making sure
that the electrons are behaving in the way that makes
whatever it is you intend to do possible. I want
to thank Chris for sending that email in and asking
(38:38):
about this, because it was fun to cover this this
this topic again and to really kind of dive in
more deeply than I had before, and I want to
encourage you guys to write in and ask about other topics.
Whether it's a technology or a company or a person,
or maybe it's someone that you want to have on
the show, either as a guest host or someone for
(39:00):
me to interview. Any of that is fine. Please let
me know, or just feedback in general about the show.
I would love to hear more from you guys. Sent
me a message. The email address is tech Stuff at
how stuff works dot com, or drop me a line
on Facebook, Twitter, or Tumblr. The handle it all three
is tech Stuff H s W. And I'll talk to
you again really soon. For more on this and thousands
(39:28):
of other topics. Works dot com
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