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4.5 Electromagnetic effects

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Question 36
a.

A rectangular coil PQRSPQRSPQRS is placed between the poles of a magnet as part of a simple electric motor.

  • The North pole of the magnet is on the left and the South pole is on the right, creating a magnetic field pointing from left to right.
  • Side PQPQPQ of the coil is on the left side, and side RSRSRS is on the right side.
  • A current flows through the coil in the direction P→Q→R→SP \to Q \to R \to SP→Q→R→S. This means the current in side PQPQPQ is flowing directly into the page (away from the observer), and the current in side RSRSRS is flowing directly out of the page (towards the observer).

(i) Determine the direction (upwards or downwards) of the magnetic force acting on side PQPQPQ and side RSRSRS.

(ii) State three ways in which the turning effect of this electric motor can be increased.

[5]
b.

In a portable device charger, a step-down transformer reduces the mains voltage of 240 V240\text{ V}240 V to a secondary voltage of 12 V12\text{ V}12 V. The transformer has 200020002000 turns on its primary coil.

Calculate the number of turns on the secondary coil.

[2]
Markscheme

4.5 Electromagnetic effects Questions

  1. IGCSE
  2. /Physics
  3. /4.5 Electromagnetic effects

275 exam-style questions on CIE IGCSE Physics 4.5 Electromagnetic effects, covering 4.5.1a Electromagnetic induction, 4.5.1b Direction of an induced e.m.f., 4.5.2 The a.c. generator, 4.5.3a Magnetic effect of a current and its applications, 4.5.3b Strength and direction of the field around wires and solenoids, 4.5.4a Force on a current-carrying conductor, 4.5.4b Force on beams of charged particles, 4.5.5 The d.c. motor, 4.5.6a Construction and operation of a transformer, 4.5.6b Turns ratio and current in a transformer, and 4.5.6c High-voltage transmission of electricity. Each one has a worked solution and a mark scheme showing where the marks go.

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