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Electricity & Electronics · No. 207 of the first 100

How does an electric motor work?

There are more electric motors than people on Earth, and nearly all of them run on one trick: push, flip, repeat.

Plate 37 — Push, flip, repeat F = BIL · commutator flips each half turn
Feed it more current, watch the rotor spin up — and catch the flip.
NS ×× = current going in · ● = coming out · red arrows = the push (F = BIL)the commutator swaps × and ● every half turn — so the push always turns the same way
PLATE 37 · PUSH, FLIP, REPEAT
Current 2.5 A
Magnet strength 2.5
Rotor speed
0rpm
Flips per turn
2commutator
A wire with current in it gets pushed sideways by a magnet. Bend the wire into a loop and the two sides get pushed in opposite directions — a perfect twist. The genius part: just as the loop levels out, a little switch (the commutator) flips the current, so the twist never changes its mind. Push, flip, push, flip — that's every fan, drill, and toy car you own.
The short answer

A magnet pushes sideways on any wire carrying current. Bend the wire into a loop and its two sides get pushed in opposite directions — a twist. Then a tiny switch flips the current every half turn, so the twist never gives up. That spinning loop is the motor in your fan, drill, and toothbrush.

What's actually happening

The discovery came in two halves. Ørsted found that current makes magnetism; Faraday, in 1821, closed the loop by showing a magnet pushes back — a current-carrying wire near a magnet feels a sideways shove, at right angles to both the current and the field. His first "motor" was a wire dangling in a cup of mercury, endlessly circling a magnet. The physics in your washing machine is that desk toy, civilised.

One straight wire only twitches. The engineering is in the loop: run the current up one side and back down the other, and the magnet shoves the two sides in opposite directions — a clean twisting force. But there's a catch the simulator shows you: once the loop turns ninety degrees, the twist has done its job and would happily stop there, rocking like a compass needle. The fix is the commutator — a split copper ring that swaps the current's direction every half turn, exactly at the dead spot. The push never learns it's been tricked. Push, flip, push, flip, thousands of times a minute.

Count the motors around you and you'll lose track fast: phone vibration, toothbrush, fans, pumps, hard drives, car windows, the compressor in the fridge. Modern brushless motors replace the mechanical flip with transistors doing the switching electronically — same trick, no sparks, which is why drones and EVs spin so smoothly. And the whole machine runs in reverse: spin the shaft yourself and the coil pushes current out instead. Every motor is a generator wearing different clothes, which is how an EV recharges its battery when it brakes.

Try it at home The ten-minute motor
  1. 1Wind 10 turns of thin enamelled wire into a coin-sized coil, leaving two straight ends as an axle. Scrape the enamel off one side only of each end.
  2. 2Rest the axle ends in two bent paperclips stuck to a battery's terminals, with a strong magnet underneath the coil.
  3. 3Give it a nudge. The half-scraped ends act as a crude commutator — current flows for half of each turn, and the coil spins. You've built Faraday's legacy from pocket junk.