11 mark
What is the capacitance of a parallel plate capacitor that holds 7.5 µC of charge with a potential difference of 2.0 V between the plates?
3.2 µF
6.1 µF
3.8 µF
10 µF
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Capacitance (AQA A Level Physics)
Exam Questions
3 hours30 questions
21 mark
The graph shows how the potential difference across a capacitor varies with the charge stored by it.
Which one of the following statements is incorrect?
the charge and potential difference are directly proportional to each other
the energy stored in the capacitor is the area under the graph
the gradient of the line equals the capacitance
the gradient of the line equals the reciprocal of the capacitance
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31 mark
What is the energy stored in a 3 µF capacitor holding a charge of 60 nC?
2.4 × 10–9 J
0.60 J
0.010 J
6.0 × 10–10 J
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41 mark
Which row in the table shows the correct units for capacitance, charge and potential difference?
| Capacitance | Charge | Potential Difference |
A B C D | C F C F | Q C C A | P V V V |
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51 mark
The graph shows how the charge stored by a capacitor varies with the potential difference across it as it is charged from a 6 V battery.
What is the energy stored in the capacitor?
9.0 × 10–5 J
1.8 × 10–4 J
5.0 × 10–6 J
4.5 × 10–4 J
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11 mark
The graph shows how the potential difference across a capacitor varies with the charge stored in it.
Which line, A to D, in the table gives the capacitance and the energy stored when the charge is 6.0 µC ?
| Capacitance / µF | Energy stored / µJ |
A B C D | 2.0 0.5 2.0 0.5 | 9.0 9.0 18 18 |
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21 mark
What is the permittivity of a dielectric between two capacitor plates 2 mm apart each with an area 4.2 m2 that has a capacitance of 14 µF?
6.7 × 10–12 F m–1
6.7 × 10–3 F m–1
6.7 × 10–6 F m–1
6.7 × 10–9 F m–1
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31 mark
A nuclear fusion device is required to deliver at least 1 GJ of energy using capacitors. If the minimum capacitance of the capacitors that are used is 30 µF, what is its largest workable potential difference?
67 TV
8.2 MV
260 kV
8.2 kV
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41 mark
A capacitor of capacitance 75 µF is fully charged through a resistor R using the circuit shown.
Which one of the following statements is correct?
The total energy taken from the battery during the charging process is 34 mJ
The charge on the capacitor is 2.5 µC
The potential difference across the resistor becomes very small (almost zero)
Both the resistor and capacitor have a potential difference greater than 1 V
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51 mark
Calculate the change in energy stored in a capacitor of capacitance 12 nF when the charge on the plates changes from 60 µC to 80 µC.
0.017 × 10–3 J
0.12 × 10–3 J
0.017 J
0.12 J
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11 mark
Which one of the following can be used as a unit for capacitance?
A2 s2 kg m–2
A2 s4 kg–1 m–2
A2 kg m
A2 s2 kg–1 m
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21 mark
A parallel–plate capacitor has square plates of length L separated by distance 3L and is filled with air as its dielectric.
A second capacitor has square plates of length 3L separated by distance 6L and is filled with a different dielectric.
Both capacitors have the same capacitance.
What is the relative permittivity of the dielectric in the second capacitor?
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31 mark
A fully charged capacitor of 4 µF is connected as shown in the circuit diagram below. The e.m.f of the cell is 3.1 V and its internal resistance is 0.5 Ω.
What is the amount of charge on the capacitor plates?
12.4 µC
11.9 µC
1.34 µC
10.5 µC
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41 mark
A capacitor of capacitance C stores an amount of energy E when the pd across it is V.
| Energy | Potential difference |
A B C D | 0.40 0.16 0.40 0.16 | 0.6 0.6 0.4 0.4 |
Which line, A to D, in the table gives the correct stored energy and pd when the charge is decreased by 60%?
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51 mark
An air–filled parallel–plate capacitor is charged from a source of emf. The electric field has a strength E between the plates. The capacitor is disconnected from the source of emf and the separation between the isolated plates is made three times smaller.
What is the final electric field between the plates?
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