Spin From a Wire - motors, generators, speakers and the induction hob

Before you start. You need The Socket Is a Waterfall - volts, amps, watts and the bill: voltage is the push, current is the flow, power is the two multiplied, and the grid’s current flips direction 50 times a second because a transformer needs it to. That lesson promised to explain why. This one does, and on the way it explains the motor in every fan, fridge and phone.

The idea in 30 seconds

A current in a coil makes a magnet you can switch and flip: an electromagnet.
A motor flips an electromagnet’s current at the right moment so the magnets keep chasing each other and the shaft keeps turning.
Induction: a magnetic field that is changing makes a current in a nearby wire, only while it changes, more when it changes faster.
A generator is a motor run backwards, and a spinning generator naturally makes alternating current.
A speaker is a motor that pushes a cone back and forth; a transformer is induction with no moving parts, which is why the grid needs alternating current.
An induction hob is a transformer whose second coil is the pan, and it heats steel far better than aluminium because the currents in steel meet more resistance.

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