Question 1

A parallel-plate capacitor consists of two metal plates of area $$A$$ separated by a distance $$d. If $$the plates carry charges $$+Q$$ and $$-Q$$, what is the magnitude of the electric field between the plates (assuming vacuum between them)?

Accepted Answer

$$E = \frac{Q}{\$$epsilon_0$$ A}$$

Question 2

Which of the following best describes the physical meaning of the constant $$\$$epsilon_0$$ (the permittivity of free space)?

Accepted Answer

It is a property of vacuum that tells us how strong electric fields are in empty space.

Question 3

A parallel-plate capacitor has circular plates of radius $$R$$ separated by a distance $$d$$ and is held at a fixed potential difference $$V. If $$the plates are moved closer together, what happens to the capacitance?

Accepted Answer

Capacitance increases

Question 4

For a parallel-plate capacitor, which of the following equations correctly gives the capacitance in terms of the plate area $$A$$, separation $$d$$, and vacuum permittivity $$\$$epsilon_0$$?

Accepted Answer

$$C = \frac{\$$epsilon_0$$ A}{d}$$

Question 5

Two capacitors, $$C_1$$ and $$C_2$$, are connected in series. Which formula gives the equivalent capacitance $$C$$?

Accepted Answer

$$\frac{1}{C} = \frac{1}{C_1$} + \frac{1}{C_2$}$$

Question 6

A capacitor of $$1\ \mu\mathrm{F} is $$connected in series with a capacitor of $$1\ \mathrm{F}. $$What is the effective capacitance of the combination?

Accepted Answer

Very close to $$1\ \mu\mathrm{F}$$

Question 7

If two capacitors are connected in parallel, how does the equivalent capacitance compare to the individual capacitances?

Accepted Answer

It is the sum of the individual capacitances.

Question 8

A parallel-plate capacitor is charged to a potential difference $$V$$ and then disconnected from the battery. If the plates are pulled farther apart, what happens to the potential difference between the plates?

Accepted Answer

It increases

Question 9

A parallel-plate capacitor is charged to a potential difference $$V$$ and then disconnected from the battery. If the plates are pulled farther apart, what happens to the charge on each plate?

Accepted Answer

It stays the same

Question 10

A parallel-plate capacitor is charged to a potential difference $$V$$ and then disconnected from the battery. If the plates are pulled farther apart, what happens to the energy stored in the capacitor?

Accepted Answer

It increases

Question 11

A parallel-plate capacitor is charged to a potential difference $$V$$ and remains connected to the battery. If the plates are pulled farther apart, what happens to the energy stored in the capacitor?

Accepted Answer

It decreases

Question 12

What is the energy stored in a capacitor with charge $$Q$$ and capacitance $$C$$?

Accepted Answer

$$U = \frac{1}{2} QV$$

Question 13

A dielectric material is inserted between the plates of a capacitor while the charge is kept constant. What happens to the potential difference across the plates?

Accepted Answer

It decreases

Question 14

Which of the following statements about the dielectric constant $$K is $$correct?

Accepted Answer

$$K is $$greater than 1

Question 15

If two capacitors, $$C_1 = 12.0$$\ \mathrm{nF}$$ and C_2$ = 6.0\ \mathrm{nF}$$, are connected in series across a $$18\ \mathrm{V}$$ battery, what is the equivalent capacitance?

Accepted Answer

$$4.0\ \mathrm{nF}$$

Question 16

In a circuit with capacitors in parallel, what is true about the potential difference across each capacitor?

Accepted Answer

It is the same for each capacitor

Question 17

Which of the following best describes the energy density $$u in $$the electric field between the plates of a parallel-plate capacitor?

Accepted Answer

$$u = \frac{1}{2} \$$epsilon_0$$ E^2$

Question 18

A capacitor is connected to a battery and then disconnected. If a dielectric is inserted between the plates, what happens to the energy stored in the capacitor?

Accepted Answer

It decreases

Question 19

A capacitor is connected to a battery and a dielectric is inserted between the plates. What happens to the charge on the plates?

Accepted Answer

It increases

Capacitors and Capacitance: Principles, Formulas, and Circuit Rules

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