Physics (AS & A Level) · Feb / March 2016 · Paper 42 · Question 7
9702
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7(a)[1]
(capacitance =) charge / potential (difference) [1]
7(b)[2]
V = V1 + V2 + V3 either Q / C = Q / C1 + Q / C2 + Q / C3 or V / Q = V1 / Q + V2 / Q + V3 / Q and so 1 / C = 1 / C1 + 1 / C2+ 1 / C3 [2]
7(c)(i)[3]
1. 1 / CT = (1 / 200) + (1 / 600) CT = 150 µF [1]
2. Q = CV = 150 × 10–6 × 12 or 600 × 10–6 × 3.0 or 200 × 10–6 × 9.0 = 1.8 × 10–3 C [1]
3. V = Q / C = 1.8 × 10–3 / 600 × 10–6 or V = [200 / (200 + 600)] × 12 = 3(.0) V [1]
7(c)(ii)[3]
energy = ½CV 2 or energy = ½QV and C = Q / V 1/2 × C × 32 = 2 × 1/2 × C × V 2 V = 2.1 V [3]
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