Quick answer: A capacitor stores charge on two plates, and its capacitance is C = Q / V in farads. This Physics 11-12 test on capacitor has 8 questions worth 20 marks, to do in 45 minutes: defining capacitance, charge and energy and combining two capacitors. The mark scheme is on a separate page; free printable PDF.
This physics grades 11-12 test on capacitor test works like a real class test. The mark scheme is on a separate page, so revise with the lesson first.
This test covers capacitance, energy, combinations of capacitors and the RC time constant. Use ε₀ = 8.85 × 10⁻¹² F/m where needed. Give every numerical answer with its unit and show the formula and the substitution.
Level: Physics grades 11-12 (A Level · IB · Class 11-12) · Curriculum: A Level 3.7.4
Capacitor test: the test questions
Question 1 Defining capacitance (2 marks)
Define capacitance and state the unit of capacitance in terms of other SI quantities.
Question 2 Charge and energy (3 marks)
A 220 µF capacitor is charged to 15 V.
- Calculate the charge stored. (1 mark)
- Calculate the energy stored. (2 marks)
Question 3 Combining two capacitors (2 marks)
Two 8.0 µF capacitors are available. Calculate the total capacitance when they are connected (a) in series and (b) in parallel.
Question 4 Reading a discharge graph (4 marks)
The graph shows the voltage across a capacitor discharging through a 20 kΩ resistor.
- State the initial voltage. (1 mark)
- Use the graph to determine the time constant. (2 marks)
- Calculate the capacitance. (1 mark)
Question 5 Charging current (2 marks)
Explain why the current in a charging RC circuit is largest at the start and falls to zero.
Question 6 Voltage after a delay (3 marks)
A 4.7 µF capacitor charged to 5.0 V discharges through a 330 kΩ resistor. Calculate the voltage after 2.0 s.
Question 7 Energy after one time constant (2 marks)
Show that the energy stored in a discharging capacitor falls to about 14 % of its initial value after one time constant.
Question 8 Unit of the time constant (2 marks)
Show that the unit of RC is the second.
