Question 1

A particle with charge $$q$$ moves at constant speed from position $$s_i to$$ $$s_f in a $$uniform electric field $$\vec{E}$$, as shown in the first image. What is the change in the particle's electric potential energy?

Accepted Answer

$$\Delta U = qE(s_f - s_i)$$

Question 2

An electron is released from rest near the negative plate of a parallel plate capacitor (see image 2). What happens to its kinetic energy as it moves toward the positive plate?

Accepted Answer

It increases because the electric field accelerates the electron toward the positive plate.

Question 3

Which equation correctly describes the electric potential at a distance $$r$$ from a point charge $$q$$?

Accepted Answer

$$V = \frac{q}{4\pi\$$epsilon_0$$ r}$$

Question 4

A negatively charged particle moves in a circular arc around a positively charged rod (see image 5). What is the sign of the work done by the rod’s electric field on the particle?

Accepted Answer

Negative

Question 5

Two like charges are released from rest and move apart (see image 7). What happens to their mechanical energy as they move?

Accepted Answer

Mechanical energy is conserved; kinetic energy increases as potential energy decreases.

Question 6

A parallel plate capacitor is charged to a potential difference $$\Delta V_C$$ and then disconnected from the battery. If the plate separation is doubled, what happens to the electric field between the plates?

Accepted Answer

The electric field remains unchanged.

Question 7

What is the electric potential inside a charged conducting sphere of radius $$R$$ and charge $$Q$$?

Accepted Answer

$$V = \frac{Q}{4\pi\$$epsilon_0$$ R}$$

Question 8

A proton is released from rest at the surface of a sphere charged to $$+1000 V. $$What equation gives the proton’s speed after it moves 1 cm away from the sphere?

Accepted Answer

$$\frac{1}{2}mv_f^2$ = 1000e$$

Question 9

Which plate in a parallel plate capacitor connected to a battery has the higher electric potential?

Accepted Answer

The plate connected to the positive terminal of the battery.

Question 10

If a negatively charged particle moves from a region of high potential to a region of low potential, what happens to its speed?

Accepted Answer

It speeds up.

Question 11

What is the potential energy of a system of three point charges $$q_1$$, $$q_2$$, and $$q_3$$ separated by distances $$r_{12}$$, $$r_{13}$$, and $$r_{23}$$?

Accepted Answer

$$U = \frac{1}{4\pi\$$epsilon_0$$} \left( \frac{q_1q_2}{r_{12}} + \frac{q_1q_3}{r_{13}} + \frac{q_2q_3}{r_{23}} \right)$$

Question 12

Which of the following best describes the electric field inside a conductor when no current is flowing?

Accepted Answer

The electric field is zero.

Question 13

A positive charge $$+Q is $$placed on a conducting sphere. Which point outside the sphere has the highest electric field strength?

Accepted Answer

The point closest to the sphere's surface.

Question 14

A positive charge $$+Q is $$placed on a conducting sphere. Which point outside the sphere has the highest electric potential?

Accepted Answer

The point closest to the sphere's surface.

Question 15

What is the electric potential at a point $$z$$ above the center of a ring of radius $$R$$ carrying charge $$Q$$?

Accepted Answer

$$V = \frac{1}{4\pi\$$epsilon_0$$} \frac{Q}{\sqrt{R^2$ + z^2$}}$$

Question 16

A capacitor is charged and then disconnected from the battery. If the plate area is doubled while keeping the separation constant, what happens to the capacitance?

Accepted Answer

The capacitance doubles.

Question 17

Which of the following statements is true about the potential energy of two charges of opposite sign as they move apart?

Accepted Answer

The potential energy increases as the charges move apart.

Question 18

If the electric field inside a conductor is zero, where does all the excess charge reside?

Accepted Answer

On the surface of the conductor.

Question 19

A battery is connected to a parallel plate capacitor, creating a potential difference $$\Delta V. $$What is the relationship between the electric field $$E$$ and the plate separation $$d$$?

Accepted Answer

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

Electric Potential and Potential Energy in Electrostatics Ch 25

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