Question 1

A metal bucket with a metal lid has zero excess charge. You place a metal ball with charge $$+q$$ inside the bucket, but the ball does not touch the bucket. At electrostatic equilibrium, what is the excess charge on the inner and outer surfaces of the bucket?

Accepted Answer

Inner surface: $$-q$$, Outer surface: $$+q$$

Question 2

A metal ball with charge $$+q is $$placed inside a metal bucket and touches the inner surface. What is the excess charge on the inner and outer surfaces of the bucket at equilibrium?

Accepted Answer

Inner surface: $$0$$, Outer surface: $$+q$$

Question 3

Which of the following best describes the function of a Faraday cage?

Accepted Answer

It shields the interior from external electric fields by redistributing charges on its surface.

Question 4

In a parallel-plate capacitor with a uniform electric field $$E$$, a charge $$q$$ moves a distance $$s$$ from the negative to the positive plate. What is the change in electric potential energy?

Accepted Answer

$$\Delta U_{elec} = qEs$$

Question 5

A negative charge $$q is $$between the plates of a parallel-plate capacitor and moves from the negative to the positive plate. What happens to its electric potential energy?

Accepted Answer

It increases.

Question 6

The electric potential energy of two point charges $$q_1$$ and $$q_2$$ separated by distance $$r is $$given by:

Accepted Answer

$$U_{elec} = \frac{k q_1$ q_2$}{r}$$

Question 7

A proton is fixed at the origin. A particle with charge $$q_2$$ \u003c 0$$ is moving away from the proton with kinetic energy K_2$. Under which condition is the particle bound to the proton?

Accepted Answer

$$K_2$$ \u003c \frac{k e |$$q_2$$|}{$$r_2$$}$$

Question 8

Two charges, $$+q$$ and $$-q$$, are fixed in position. A third charge is added at a point equidistant from both. How does the electric potential energy of the system change?

Accepted Answer

Potential energy does not change.

Question 9

The electric potential energy of a dipole $$\vec{p} in a $$uniform electric field $$\vec{E} is$$:

Accepted Answer

$$U_{elec} = -\vec{p} \cdot \vec{E}$$

Question 10

A dipole is placed in two identical uniform electric fields, but in opposite directions. How do their potential energies compare?

Accepted Answer

$$U_A \u003c U_B$$

Question 11

The electric potential $$V at a $$distance $$r$$ from a point charge $$q is$$:

Accepted Answer

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

Question 12

Two metal spheres, A and B, are separated by a large distance. The radius of A is twice that of B. If both have the same electric potential at their surfaces, what is the ratio of their charges $$Q_A/Q_B$$?

Accepted Answer

$$Q_A = 2 Q_B$$

Question 13

The electric potential at a point due to several point charges is:

Accepted Answer

$$V = \sum_i \frac{q_i}{4 \pi \$$epsilon_0$$ r_i}$$

Question 14

Three arrangements of two protons are shown, each with a point P at the same distance from both protons. How does the net electric potential at P compare for the three cases?

Accepted Answer

$$V_A = V_B = V_C$$

Question 15

The relationship between electric potential difference and electric field is given by:

Accepted Answer

$$\Delta V = - \int \vec{E} \cdot d\vec{s}$$

Question 16

The electric field in the $$s-$$direction can be found from the potential by:

Accepted Answer

$$E_s = -\frac{dV}{ds}$$

Question 17

A graph of $$V(x) is $$given. For $$x  x_0$, V$ decreases linearly. Which graph best represents E_x$ as a function of x$?

Accepted Answer

$$E_x = 0$$ for $$x  x_0$

Question 18

Three points (A, B, C) are midway between metal rods with a constant potential difference between the rods. At which point is the electric field magnitude greatest?

Accepted Answer

Point C, where the rods are closest together.

Question 19

An electron is released from rest just above the negative plate of a parallel-plate capacitor with a potential difference of $$2.4 	imes 10^4$ V. What is its speed when it reaches the positive plate? (Electron charge e = 1.6$$ 	imes $$10^{-19} C$$, mass $$m = 9.1 	imes 10$$^{-31}$$ kg)

Accepted Answer

$$9.2 	imes 10^7$ m/s

Question 20

Which of the following best describes how an electrostatic precipitator removes smoke particles from waste gas in a coal-burning power plant?

Accepted Answer

Smoke particles pick up a negative charge and are attracted to positively charged collecting plates.

Electric Potential, Potential Energy, and Field: Study Notes for Chapters 25 & 26

Study Guide - Practice Questions

Study Guide - Flashcards