State Fleming’s left hand rule. Name one device that works on the basis of this rule.

Answer: Stretch the thumb, forefinger and middle finger of the left hand mutually perpendicular; if the forefinger shows the magnetic field and the middle finger the current, the thumb shows the force (motion) on the conductor. Device: electric motor.

• Forefinger → direction of the magnetic field.
• Middle finger → direction of the current in the conductor.
• Thumb → direction of the force on the conductor, i.e. the direction in which it moves.

The electric motor works on this rule (it converts electrical energy into mechanical energy).