# Worksheet: Parallel-Plate Capacitors

In this worksheet, we will practice relating the capacitance of parallel-plates to charge, potential difference, and electric field strength.

Q1:

A sweater made of a synthetic material becomes statically charged by friction. The sweater and the skin beneath it act as a 55 nF capacitor. The person wearing the sweater comes into contact with a conducting surface that carries away the charge stored in the capacitor by producing a 220 mV spark.

How much charge was stored in the capacitor?

• A C
• B C
• C C
• D C
• E C

How many excess electrons were stored by the sweater? Use the value C for the charge of an electron.

• A
• B
• C
• D
• E

Q2:

At the instant when the current through the resistor in the circuit shown in the diagram is 0.69 A, what charge is stored by the 22 µF capacitor in the circuit? • A C
• B C
• C C
• D C
• E C

Q3:

Which of the following formulas correctly relates the charge stored by a parallel plate capacitor to the capacitance of the capacitor, the permittivity of the medium between the plates, and the potential difference across the plates?

• A
• B
• C
• D
• E

Q4:

A parallel plate capacitor has square plates with sides 20 cm long, 7.5 mm apart. The potential difference across the plates is 35 V and the permittivity of the space between the plates is C2/N⋅m2. What is the charge stored by the capacitor?

• A C
• B C
• C C
• D C
• E C

Q5:

The capacitor in the circuit shown in the diagram stores a charge of 3.6 mC. What is the potential difference V across the resistor? Q6:

An 11.5 µF parallel plate capacitor stores 888 µC of charge. What is the potential difference across its plates?

Q7:

A 475 µF parallel plate capacitor has a potential difference of 12.5 V across its plates. What charge does the capacitor store?

Q8:

A parallel-plate capacitor has square plates with sides 15 cm long, 2.5 cm apart. Find the capacitance of the capacitor. Use the value C/N⋅m2 for the permittivity of the space between the plates, and answer to two significant figures.

• A F
• B F
• C F
• D F
• E F

Q9:

The capacitor in the circuit shown in the diagram stores a charge of 160 µC. What is the capacitance of the capacitor? Q10:

A 2.1 nF parallel plate capacitor has square plates with sides 25 cm long, 1.5 cm apart. Find the permittivity of the space between the plates.

• A C2/N⋅m2
• B C2/N⋅m2
• C C2/N⋅m2
• D C2/N⋅m2
• E C2/N⋅m2

Q11:

A parallel plate capacitor has square plates with a 1.25 V/m uniform electric field between them. The permittivity of the space between the plates is C2/N⋅m2. What is the charge density of the plates?

• A C/m2
• B C/m2
• C C/m2
• D C/m2
• E C/m2

Q12:

A 36 µF parallel plate capacitor stores 240 µC of charge. There is a uniform electric field between the plates of the capacitor. The plates are 6.5 cm apart. What is the strength of the electric field?

Q13:

A parallel plate capacitor has a potential difference of 75 V across its plates. 15 µC of charge is stored by the capacitor. What is the capacitance of the capacitor?

Q14:

A cloud initially holds a 64 C negative charge as it floats above neutral ground. The cloud completely discharges in a lightning strike that produces a 430 kV bolt. What is the capacitance of the cloud and land directly below it? 