Question 1

Which of the following best describes the relationship between electric field lines and equipotential lines as shown in the first image?

Accepted Answer

Electric field lines are always perpendicular to equipotential lines.

Question 2

In the second image, the electric field $$E = 1000\ \mathrm{V/m}$$ points to the right. If point A is to the left of point B by $$7.0\ \mathrm{cm}$$, what is the potential difference $$\Delta V = V_B - V_A$$?

Accepted Answer

$$\Delta V = -70\ \mathrm{V}$$

Question 3

A battery is connected to a parallel-plate capacitor as shown in the fourth image. Which of the following statements is correct about the direction of current and the movement of positive ions?

Accepted Answer

Current flows from the positive to the negative terminal, and positive ions move toward the negative terminal inside the battery.

Question 4

The capacitance of a parallel-plate capacitor is given by $$C = \$$varepsilon_0$$ \dfrac{A}{d}. $$Which change will increase the capacitance?

Accepted Answer

Increasing the plate area $$A$$

Question 5

A dielectric material with dielectric constant $$\kappa is $$inserted between the plates of a capacitor while it remains connected to a battery. What happens to the charge stored on the capacitor?

Accepted Answer

The charge increases.

Question 6

Refer to the table of dielectric constants and strengths. Which material would allow the highest voltage across a capacitor before breakdown occurs?

Accepted Answer

Teflon

Question 7

A $$90.0\ \mu\mathrm{F}$$ capacitor in a defibrillator supplies $$6500\ \mathrm{W} of $$power for $$5.0\ \mathrm{ms}. To $$what voltage is the capacitor charged? (Use $$U = \frac{1}{2}C\Delta V^2$ and P$$ = \frac{\Delta U}{\Delta t}$$)

Accepted Answer

$$\Delta V = 1200\ \mathrm{V}$$

Question 8

Which of the following best explains why lightning occurs, as shown in the image of clouds and lightning?

Accepted Answer

The electric field between clouds and the ground exceeds the dielectric strength of air, causing ionization.

Question 9

If three capacitors $$C_1 = 2$$\ \mu\mathrm{F}$$, C_2$ = 4\ \mu\mathrm{F}$$, and $$C_3 = 6$$\ \mu\mathrm{F}$$ are connected in series, what is the equivalent capacitance?

Accepted Answer

$$C_{eq} = 1.09\ \mu\mathrm{F}$$

Question 10

A $$75.0\ \mu\mathrm{F}$$ capacitor is available, but you need a total capacitance of $$50.0\ \mu\mathrm{F}. $$What value capacitor should you connect in series with the $$75.0\ \mu\mathrm{F}$$ capacitor to achieve this?

Accepted Answer

$$C = 25.0\ \mu\mathrm{F}$$

Question 11

Which of the following statements about the energy stored in a capacitor is correct?

Accepted Answer

The energy stored is $$U = \frac{1}{2}C\Delta V^2$ and is stored in the electric field between the plates.

Question 12

If the distance between the plates of a parallel-plate capacitor is doubled while keeping the area and charge constant, what happens to the electric field between the plates?

Accepted Answer

The electric field remains the same.

Question 13

Which of the following is a correct statement about the effect of inserting a dielectric into a charged, isolated capacitor?

Accepted Answer

The capacitance increases and the voltage decreases.

Question 14

A parallel-plate capacitor has plates of area $$A$$ and separation $$d. If $$the potential difference across the plates is $$\Delta V$$, what is the magnitude of the electric field between the plates?

Accepted Answer

$$E = \dfrac{\Delta V}{d}$$

Question 15

Which of the following best describes the effect of a dielectric on the electric field inside a capacitor, as shown in the images?

Accepted Answer

The dielectric creates an induced field that opposes and reduces the overall electric field.

Question 16

In a circuit with capacitors in parallel, which of the following is true?

Accepted Answer

The voltage across each capacitor is the same.

Question 17

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

Accepted Answer

The stored energy decreases.

Question 18

Which of the following is a practical application of capacitors?

Accepted Answer

Camera flash

Electric Potential and Capacitance: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards