Capacitors test with answers for AP Physics 2 (free PDF download)

Quick answer: A capacitor stores charge on two plates separated by an insulator, with capacitance C = Q/V in farads. This AP Physics 2 test on capacitors has 8 questions worth 20 marks, to do in 45 minutes: capacitance, parallel plates and energy in a flash unit. The mark scheme is on a separate page; free printable PDF.

This test covers capacitance, parallel plates, stored energy and dielectrics at AP Physics 2 level. Firstly, use ε₀ = 8.85 × 10⁻¹² F/m. A calculator is allowed. Also, show every step, give units with each result, and state clearly which quantity stays constant when you insert a dielectric.

Level: AP Physics 2 (algebra-based) · Curriculum: AP P2 Unit 10

Time: 45 minutes · 8 questions · Total: 20 marks · Calculator allowed

Contents

Question 1 Capacitance (2 marks)

A capacitor stores 12 μC when connected to 3.0 V.

Firstly, define capacitance. (1 mark)
Then calculate its capacitance. (1 mark)

Question 2 Parallel plates (3 marks)

A parallel-plate capacitor has plates of area 0.030 m² separated by 0.50 mm of air. Use ε₀ = 8.85 × 10⁻¹² F/m.

Firstly, calculate its capacitance. (2 marks)
Then state the effect on C of doubling the separation. (1 mark)

Question 3 Energy in a flash unit (3 marks)

A 220 μF capacitor is charged to 24 V. Then calculate the charge stored and the energy stored. (3 marks)

Question 4 Battery stays connected (3 marks)

Firstly, a 2.0 μF capacitor is connected to a 12 V battery. A dielectric with κ = 3.0 fills the gap with the battery still connected. Then calculate the new capacitance and the charge before and after. (3 marks)

Question 5 Isolated capacitor (3 marks)

You disconnect a charged capacitor from its battery and then insert a dielectric. Afterwards, state what happens to the charge, capacitance, voltage and stored energy, and explain the energy change. (3 marks)