2024 · M/J · 9702/41 | Q6

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Question (6 of 10)10 marks · Practise this topic →

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Available practice: 94 of 100 marks. Parts 3(a)(i), 7(a), 8(a) await marking support. Scores cover available parts only.

Fig. 6.1 shows a capacitor of capacitance C connected in series with a resistor of resistance R. Initially the switch is open and there is a p.d. of 12 V across the capacitor. At time t = 0, the switch is closed so that there is a current I in the resistor. Fig. 6.2 shows the variation of I with t.

(a)Explain the shape of the line in Fig. 6.2.

Fig. 6.1 — see the question text for what it shows

Fig. 6.2 — see the question text for what it shows

Answer guidance

Explain Give reasons, not just what happens. Each distinct reason is usually worth a mark.

[3 marks]

A capacitor of capacitance C is connected in series with a resistor of resistance R through a switch . Initially the switch is open and there is a p.d. of 12 V across the capacitor. At t = 0 the switch is closed so that there is a current I in the resistor.

(b)(i)Use Fig. 6.2 to determine resistance R.

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Using You must use the thing it names. An answer that reaches the right value another way may not score.

[2 marks]

A capacitor of capacitance C is discharged through a resistor of resistance R when a switch is closed at t = 0, the initial p.d. across the capacitor being 12 V.

(b)(ii)Use Fig. 6.2 to determine the time constant τ of the circuit in Fig. 6.1.

Answer guidance

Using You must use the thing it names. An answer that reaches the right value another way may not score.

[3 marks]

A capacitor of capacitance C is discharged through a resistor of resistance R; from the current–time graph the resistance R and the time constant τ of the circuit have been determined.

(c)Use your answers in (b) to determine capacitance C.

Answer guidance

Using You must use the thing it names. An answer that reaches the right value another way may not score.

[2 marks]

9702/41/M/J/24Cambridge International AS & A Level Physics 9702 · May/June 2024 · Paper 4 variant 1 · Question 6