Motors
A toy motor is a coil that spins in a magnetic field.
- A coil sits between two poles. At rest.
- Current flows in. One side is pushed into the page, the other out. The coil spins. A motor.
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The rule
A motor changes electrical energy into motion. A split-ring commutator reverses the current every half turn. That keeps the coil turning the same way.
Motor. A coil sits in a field. The current goes down one side and up the other. The left-hand rule then gives opposite pushes. So the coil turns.
A split-ring commutator is a ring cut into two halves. It reverses the current every half turn. Without it, the coil would stop and swing back.
| Part | Job |
|---|---|
| Coil | Carries the current. The field pushes its sides. |
| Magnet | Makes the field that pushes the sides. |
| Split ring | Reverses the current every half turn. |
A fan and a pump use motors.
Worked example
The field runs from N to S, left to right. On the left side the current goes into the page. The left-hand rule gives a push down. On the right side the current comes out. The push is up. Left side down, right side up: the coil turns anticlockwise.