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Chapter 11 Practice Paper: Electromagnetic Induction — question paper

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Secondary 4 · Physics (G2 / G3)

Chapter 11 Practice Paper

Electromagnetic Induction

Duration: 40 minutes
Total: 30 marks
Name:
Class:
Register No.:
Date:

READ THESE INSTRUCTIONS FIRST

  • Write your name, class and register number in the spaces at the top of this page.
  • Answer all questions.
  • Give numerical answers correct to 3 significant figures unless stated otherwise, with units where a quantity is calculated.
  • The number of marks is given in brackets [ ] at the end of each question or part question.
  • The total number of marks for this paper is 30.

Original practice material written for the MOE Physics syllabus. It is not an official MOE or school examination paper. Inducing an e.m.f. by changing magnetic flux linkage, Faraday’s law and Lenz’s law, Fleming’s right-hand rule, factors affecting the induced e.m.f., the simple a.c. generator, transformer action Vs/Vp = Ns/Np, ideal transformer power, energy losses, and high-voltage power transmission.

For Examiner’s Use
Section A/ 10
Section B/ 20
Total/ 30

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

  1. 1

    A magnet rests inside a coil that is connected to a centre-zero voltmeter. The voltmeter reads zero because

    1. Athe magnet is too weak to induce anything
    2. Bno flux passes through the coil at all
    3. Cthe flux linkage through the coil is not changing
    4. Dthe coil has too few turns
    ( )
  2. 2

    A bar magnet is pushed north-pole-first into a solenoid. The induced current in the solenoid flows so that the near end becomes

    1. Aa south pole, attracting the magnet and speeding it up
    2. Ba north pole, opposing the magnet’s approach
    3. Cno pole at all, since the magnet is still outside
    4. Da north pole that attracts the magnet in
    ( )
  3. 3

    Mains electricity at 230 V feeds the 1150-turn primary coil of a transformer. The secondary coil has 40 turns. The e.m.f. across the secondary is

    1. A0.80 V
    2. B6.6 V
    3. C8.0 V
    4. D66 V
    ( )
  4. 4

    The core of a transformer is laminated to reduce

    1. Aresistance of the windings
    2. Beddy currents in the core
    3. Cleakage of field lines
    4. Dhysteresis of the magnet
    ( )
  5. 5

    Electricity is transmitted at very high voltage mainly so that

    1. Athe current in the cables is small and the I²R heating loss is low
    2. Bthe cables carry more total power than they are rated for
    3. Celectrons travel faster along the cables
    4. Dthe transformers can be switched off at night
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

  1. 1

    A bar magnet is moved into, and then held stationary inside, a coil connected to a sensitive centre-zero voltmeter.

    1. (a)

      State what the voltmeter shows as the magnet moves into the coil, and explain why.

      [3]
    2. (b)

      State the voltmeter reading when the magnet is held stationary inside the coil, with a reason.

      [2]
    3. (c)

      State two ways to make the deflection larger when the magnet is withdrawn.

      [1]
  2. 2

    An ideal transformer has 500 primary turns and 25 secondary turns. The primary is connected to a 230 V, 50 Hz supply and a 12 V, 24 W lamp is connected across the secondary.

    1. (a)

      Calculate the secondary e.m.f. and state whether the transformer steps up or steps down.

      secondary e.m.f. =V[2]
    2. (b)

      The lamp runs at its rating. Calculate the secondary current.

      secondary current =A[2]
    3. (c)

      Take the transformer to be perfectly efficient and calculate the current drawn from the 230 V supply.

      [3]
  3. 3

    A power station generates 24 kW and must send it along a cable of total resistance 2.0 Ω to a distant village.

    1. (a)

      Calculate the cable current if the power is sent at 240 V, and the power lost as heat in the cable.

      [3]
    2. (b)

      The sending voltage is raised to 24 kV. Find the new cable current and the new power wasted in the cable.

      [2]
    3. (c)

      Explain, using your answers, why transmission voltages are made very high.

      [2]

— End of paper —