Physics (AS & A Level) · May / June 2025 · Paper 42 · Question 7

Fig. 7.1 shows a circuit containing a capacitor of capacitance C and a resistor of resistance R. C R Fig. 7.1 Initially, the switch is open and the potential difference (p.d.) across the capacitor is 12 V. The switch is closed at time t = 0 and the capacitor discharges through the resistor. Fig. 7.2 shows the variation of the charge Q on the capacitor with the p.d. VC across the capacitor as the capacitor discharges. Fig. 7.3 shows the variation of the current I in the resistor with the p.d. VR across the resistor as the capacitor discharges. 0 0 4 8 4 8 12 VC / V Q / mC 0 0 1 2 4 8 12 VR / V I / mA Fig. 7.2 Fig. 7.3

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