Question 1
The initial potential difference across a capacitor is V0. The capacitor discharges through a circuit of time constant T. The base of natural logarithms is e.
What is the potential difference across the capacitor after time T?
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Question 2
An uncharged capacitor is connected to a power supply which supplies a constant current of 10 μA.
After 100 ms, the potential difference across the capacitor is 5.0 kV.
What is the capacitance of the capacitor?
2.0 × 10−10 F
4.0 × 10−10 F
2.5 × 109 F
5.0 × 109 F
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Question 3
A 10 μF capacitor stores 4.5 mJ of energy.
It then discharges through a 25 Ω resistor.
What is the maximum current during the discharge of the capacitor?
1.2 A
18 A
30 A
36 A
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Question 4
A parallel-plate capacitor is fully charged and then disconnected from the power supply.
A dielectric is then inserted between the plates.
Which row correctly identifies the charge on the plates and the electric field strength between the plates?
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Question 5
A capacitor of capacitance C has a charge of Q stored on the plates. The potential difference between the plates is doubled.
What is the change in the energy stored by the capacitor?
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Question 6
A capacitor consists of two parallel square plates of side l separated by distance d.
The capacitance of the arrangement is C.
What is the capacitance of a capacitor with square plates of side 2l separated by a distance ?
C
2C
4C
8C
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Question 7
A capacitor of capacitance 120 µF is charged and then discharged through a 20 kΩ resistor.
What fraction of the original charge remains on the capacitor 4.8 s after the discharge begins?
0.14
0.37
0.63
0.86
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Question 8
Which of the following statements about a parallel plate capacitor is incorrect?
the capacitance of the capacitor is the amount of charge stored by the capacitor when the pd across the plates is 1 V
A uniform electric field exists between the plates of the capacitor
the charge stored on the capacitor is inversely proportional to the pd across the plates
the energy stored when the capacitor is fully charged is proportional to the square of the pd across the plates
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Question 9
A 1.0 µF capacitor is charged for 20 s using a constant current of 10 µA.
What is the energy transferred to the capacitor?
5.0 × 10–3 J
1.0 × 10–2 J
2.0 × 10-2 J
4.0 × 10–2 J
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Question 10
A 1.0 µF capacitor initially stores 15 µC of charge. It then discharges through a 25 Ω resistor.
What is the maximum current during the discharge of the capacitor?
0.60 mA
1.2 mA
0.60 A
1.2 A
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