Question 1
- State how a magnetizing force is:
- increased in a material;
- reversed in a material.
- Explain the term electromagnetic induction.
The expected answers were:
(a) (i) Magnetizing force can be increased by
- increasing the current in the coil
- moving the magnet or coil faster during electromagnetic induction (faraday’ experiment).
(ii) Magnetizing force can be reversed by
- reversing the polarity of the supply voltage across the coil
- reversing the direction of motion of the magnet or coil.
(b) Electromagnetic induction
Electric current or voltage is produced whenever there is relative motion between the coils and the magnetic field. The induced e.m.f. or current depends on, the relative motion, strength of the magnetic field, and the number of turns in the coil.
(c) Applications of electromagnetism
- Transformer
- Electric motor
- Electric bells
- Loud speakers
- Telephone earpiece
- Relays
- Moving coil galvanometer
- Magnetic levitation train
- Implants and magnetic resonance imaging (MRI)
- Electromagntic therapy
- X-ray equipments
- Scanner in hospitals
Many of the candidates that attempted this question could only define electromagnetic induction and listed two applications of electromagnetism.