Why do some plugs have one wider prong than the other normal one while others have two normal prongs with the same size?

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What I’m talking about is, for example, a keurig coffee machine having two differently shaped prongs where one prong is bigger and wider than the other, so you have to insert the wider prong into the wider port.

However, something like a phone adapter doesn’t have this, and the two prongs are the same size and shape.

Why is this?

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14 Answers

Anonymous 0 Comments

The different sizes of the blades is to enforce polarity. One of the blades is “hot” and one is “neutral”. This is both a safety thing and an electrical design thing.

For devices without a dedicated ground pin, the chassis of the appliance may be grounded to the neutral in which case it is important to ensure that the neutral blade of the plug is in the neutral slot of the socket (otherwise, touching it would be dangerous). A device may also simply require the correct polarity to function correctly.

For some devices, the polarity simply does not matter.

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