State Fleming's left-hand rule. Describe an activity to show the force on a current-carrying wire placed in a magnetic field, and name one device that uses this force.

1. 1 · State the rule. Stretch the thumb, first finger and middle finger of the left hand at right angles. First finger: field; middle finger: current; thumb: force.
2. 2 · Set up the activity. Hang a copper wire between the poles of a horseshoe magnet, at right angles to the field, and join it to a battery and switch.
3. 3 · Draw it. [Sketch: horseshoe magnet, wire between the poles, arrows for field, current and force]
4. 4 · Observe. When the current flows, the wire is pushed up. Reversing the current or the poles pushes it down.
5. 5 · Give the factors. A larger current or a stronger magnet gives a larger force.
6. 6 · Name a use. The electric motor in a ceiling fan uses this force.

Scoring tip: Name all three fingers and what each shows. Examiners give the rule mark only when all three are matched correctly.