WEBVTT - Why do electric plugs have holes?

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<v Speaker 1>Welcome to brain Stuff from house stuff works dot com

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<v Speaker 1>where smart happens. Hi Am Marshall Brain with today's question,

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<v Speaker 1>why do the two flat prongs on plugs for most

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<v Speaker 1>electrical appliances have holes in them? If you unplug any

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<v Speaker 1>appliance in your house, there's a nine percent chance that

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<v Speaker 1>the two flat prongs have holes in them. There are

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<v Speaker 1>three reasons for those holes. First, if you were to

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<v Speaker 1>take a part in outlet and look at the contact

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<v Speaker 1>wipers that those prongs slide into, you would find that

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<v Speaker 1>they have bumps on them. These bumps fit into the

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<v Speaker 1>holes so that the outlet can grip the plugs prongs

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<v Speaker 1>more firmly. This detenting prevents the plug from slipping out

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<v Speaker 1>of the socket due to the weight of the plug

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<v Speaker 1>in the cord. It also improves the contact between the

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<v Speaker 1>plug and the outlet. Second, electrical devices can be factory

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<v Speaker 1>sealed or locked out by the manufacturer or owner using

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<v Speaker 1>a plastic tie or a small padlock that runs through

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<v Speaker 1>one or both of those prong holes. For example, a

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<v Speaker 1>manufacturer might apply a plastic band through the hole and

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<v Speaker 1>attach a tag to it that says you must do

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<v Speaker 1>blah blah blah before plugging in this device. The user

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<v Speaker 1>can't plug in the device without removing the tags, so

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<v Speaker 1>the user is sure to see the instructions. Third, there's

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<v Speaker 1>also a small savings and raw materials for the manufacturer

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<v Speaker 1>of the actual plug prong. Every little bit helps. It's

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<v Speaker 1>been reported that really old outlets used captive ball bearings

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<v Speaker 1>in coil springs for the detent, but today it's done

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<v Speaker 1>with a bump on a springy copper contact. Do you

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<v Speaker 1>have any ideas or suggestions for this podcast? If so,

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<v Speaker 1>please send me an email at podcast at how stuff

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<v Speaker 1>works dot com. For more on this and thousands of

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<v Speaker 1>other topics, go to how stuff works dot com and

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