O-LevelPhysicsMagnetism5054/22 · Oct/Nov 2024 · Q79 Marks

The frequency of an alternating current mains electricity supply is 50 Hz. The maximum voltage of the supply is 300 V.

(a)Using the axes in Fig. 7.1, sketch a graph to show how the voltage of the supply varies in a time of 0.05 s. [Figure 7.1][3]
(b)(i)Fig. 7.2 shows the mains power supply connected to the primary coil of a transformer. The primary coil consists of 750 turns. [Figure 7.2] The core of the transformer is made from iron. Explain why iron is a suitable material for the core of the transformer.[1]
(b)(ii)Explain why there is a voltage across the secondary coil.[3]
(b)(iii)There are 60 turns on the secondary coil. Calculate the maximum value of the voltage across the secondary coil. maximum voltage = ..................................................... V[2]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2024). The mark or mark type is shown in brackets.

[1] sinusoidal curved line drawn on Fig. 7.1
[1] at least one sinusoidal cycle of period 0.020 (s) on Fig. 7.1
[1] 2.5 sinusoidal cycles of period 0.020 (s) and amplitude of 300 V on at least one cycle on Fig. 7.1
[1] it is a temporary magnetic material
[1] (alternating / changing) current in primary coil
[1] alternating / changing magnetic field (in core / in secondary coil)
[1] voltage / e.m.f. induced (in secondary coil)
[1] (Vₛ =) NₛVₚ / Nₚ or 60 × 300 / 750
[1] 24 (V)

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