How can an electric toothbrush recharge its batteries?

An electric toothbrush gets power from its base without the help of metal contacts. Find out how this sealed system works in the following podcast from HowStuffWorks.com.

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Episode Transcript

Speaker 1 (00:00):
Welcome to Brainstuff from house stuff works dot com where
smart happens. Hi'm Marshall Brain with today's question, how can
an electric toothbrush recharge its batteries when there are no
metal contacts between the toothbrush and the recharging base. If

(00:24):
you own an electric toothbrush, there's a good chance that
it has a completely sealed toothbrush unit. The toothbrush rests
on the charger without any metal contacts to connect the
toothbrush to the base. This has the great advantage of
allowing the toothbrush to be completely sealed so that water
can't enter through those exposed contacts. It also avoids any

(00:47):
problems with water getting into the contacts and shorting out
the charger. This sort of sealed arrangement is called inductive charging. Essentially,
the toothbrush and the base form a two part transformer,
with the base having one part of the transformer and
the toothbrush having the other. When you slide the toothbrush

(01:07):
onto that base, the complete transformer is created and charge
can flow to the batteries. The base contains one of
the coils of the transformer and the metal bar the
toothbrush contains the second coil. When you drop the toothbrush
onto the base, you create the complete transformer. Do you
have any ideas or suggestions for this podcast? If so,

(01:31):
please send me an email at podcast at how stuff
works dot com. For more on this and thousands of
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