O-LevelPhysicsMagnetism5054/22 · May/June 2023 · Q87 Marks

Fig. 8.1 shows a step-down transformer used to operate an electric bell. [Figure 8.1]

(a)State the material used for the core of the transformer.[1]
(b)A current in the primary coil produces a magnetic field in the core. Explain how an alternating voltage is produced in the secondary coil.[3]
(c)The transformer has 4600 turns on the primary coil which is connected to a mains supply of 230 V. An output of 5.0V is used to operate the bell. Calculate the number of turns needed on the secondary coil. number of turns = .................................................[2]
(d)State one change that can be made to the transformer shown in Fig. 8.1 so that it can be used as a step-up transformer.[1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

[B1] (soft) iron
[B1] input voltage or input current is alternating
[B1] changing (magnetic) field (in primary causes changing magnetic field in secondary) (alternating emf is) induced (in secondary coil)
[B1] or (magnetic) field lines cut secondary
[C1] (Ns=) 4600 × 5/230 or Vp / Vs = Np / Ns in any form
[A1] 100
[B1] reverse the coils OR connect the input to the secondary / right-side coil OR secondary has more turns than primary / more than 4600 (with same number on primary)

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