Available practice: 71 of 75 marks. Parts 5(a)(ii), 5(b)(i), 11(a) await marking support. Scores cover available parts only. Theory Paper 2: Section A is compulsory and Section B offers a choice of two questions. Four published mark-scheme discrepancies across the two variants are held from automatic marking.
(a)A transformer and a diode are used to charge a battery. Fig. 8.1 shows the transformer, which contains a soft-iron core and two coils. The primary coil is connected to the 240 V a.c. mains supply. The secondary coil is connected in series with the diode and the battery. Explain why an electromotive force (e.m.f.) is induced in the secondary coil.
Answer guidance
Explain Give reasons, not just what happens. Each distinct reason is usually worth a mark.
[2 marks]
(b)A transformer and a diode are used to charge a battery. Fig. 8.1 shows the transformer, which contains a soft-iron core and two coils. The primary coil is connected to the 240 V a.c. mains supply. The secondary coil is connected in series with the diode and the battery. The e.m.f. induced in the secondary coil is less than 240 V. Suggest why.
Answer guidance
Suggest More than one answer may be acceptable, so long as it is consistent with the physics.
[1 mark]
(c)A transformer and a diode are used to charge a battery. Fig. 8.1 shows the transformer, which contains a soft-iron core and two coils. The primary coil is connected to the 240 V a.c. mains supply. The secondary coil is connected in series with the diode and the battery. Suggest why steel is not used as the core of a transformer.
Answer guidance
Suggest More than one answer may be acceptable, so long as it is consistent with the physics.
[1 mark]
(d)A transformer and a diode are used to charge a battery. Fig. 8.1 shows the transformer, which contains a soft-iron core and two coils. The primary coil is connected to the 240 V a.c. mains supply. The secondary coil is connected in series with the diode and the battery. Describe the action of the diode.
Answer guidance
Describe Say what happens, in order. Reasons are not required unless the question also asks why.
[1 mark]
5054/22/M/J/16Cambridge O Level Physics 5054 · May/June 2016 · Paper 2 variant 2 · Question 8