Higher: the motor effect

The idea

When a current-carrying conductor is placed in a magnetic field, the magnet and conductor exert a force on each other: the motor effect. Fleming's left-hand rule gives the direction: first finger = field, second finger = current, thumb = motion (force). For a wire at right angles to the field, the size of the force is F = BIl, where B is the magnetic flux density in tesla, I the current and l the length of wire in the field. In an electric motor, forces on opposite sides of a coil act in opposite directions, so the coil rotates.

1. Use F = BIl with tesla, amps and metres.
2. Apply Fleming's left-hand rule for direction.
3. Explain the rotation of a coil.

Watch out The force is zero if the wire is parallel to the magnetic field.