Question 1

A plastic rod is rubbed with wool, causing the rod to become negatively charged. What happens to the wool?

Accepted Answer

The wool becomes positively charged because electrons are transferred from the wool to the rod.

Question 2

Which of the following best describes polarization in an insulator when placed near a charged object?

Accepted Answer

The charges within the insulator rearrange, causing one side to become slightly positive and the other slightly negative.

Question 3

Four point charges, each of magnitude $$q$$, are placed at the corners of a square of side $$a. $$What is the magnitude of the net force on one charge due to the other three?

Accepted Answer

$$F = \frac{kq^2$}{a^2$} \left( \sqrt{2} + 1 \right)$$

Question 4

Three charges are placed at the vertices of an equilateral triangle. If each charge is $$+q$$ and the side length is $$a$$, what is the direction of the net force on one charge?

Accepted Answer

The net force points directly away from the center of the triangle.

Question 5

A charge $$q is $$placed in a region where the electric field is $$\vec{E} = 3\hat{i} + 4\hat{j} N/C. $$What is the magnitude of the force on the charge?

Accepted Answer

$$F = q 	imes 5 N$$

Question 6

Which statement about the electric field is correct?

Accepted Answer

The electric field is defined as the force per unit positive charge.

Question 7

According to Coulomb's Law, what happens to the force between two point charges if the distance between them is doubled?

Accepted Answer

The force is reduced to one-fourth.

Question 8

Given the function $$F(q) = aq^2$ + bq$$, for what value of $$q is $$the force maximized?

Accepted Answer

$$q = -\frac{b}{2a}$$

Question 9

Given the electric field function $$E(x) = -2x^2$ + 4x$$, at what value of $$x is $$the electric field maximized?

Accepted Answer

$$x = 2$$

Question 10

What is the electric field at the center of a ring of radius $$R$$ carrying a total charge $$Q$$?

Accepted Answer

$$E = 0$$

Question 11

A uniformly charged line of length $$L$$ and total charge $$Q is $$placed along the x-axis. What is the electric field at a point $$P$$ located a distance $$a$$ from one end of the line along the axis?

Accepted Answer

$$E = \frac{kQ}{L} \left( \frac{1}{a} - \frac{1}{a+L} \right)$$

Question 12

A cube has a uniform electric field passing through it. What is the net electric flux through the cube?

Accepted Answer

The net flux is zero.

Question 13

A plane of area $$A is $$placed perpendicular to a uniform electric field $$E. $$What is the electric flux through the plane?

Accepted Answer

$$\Phi = EA$$

Question 14

Using Gauss's Law, what is the electric field outside a long, uniformly charged rod with linear charge density $$\lambda$$?

Accepted Answer

$$E = \frac{\lambda}{2\pi\$$epsilon_0$$ r}$$

Question 15

What happens to the electric field inside a conductor in electrostatic equilibrium?

Accepted Answer

The electric field is zero everywhere inside the conductor.

Question 16

Which statement about Gauss's Law is correct?

Accepted Answer

Gauss's Law relates the net electric flux through a closed surface to the charge enclosed.

Question 17

A hollow conducting sphere is given a net charge. Where does the charge reside?

Accepted Answer

The charge resides entirely on the outer surface.

Question 18

A point charge $$q is $$placed at the center of a cube. What is the electric flux through one face of the cube?

Accepted Answer

$$\Phi = \frac{q}{6\$$epsilon_0$$}$$

Question 19

Which of the following is NOT a consequence of Gauss's Law?

Accepted Answer

The electric field inside a uniformly charged shell is nonzero.

Study Guide: Electric Charge, Electric Field, and Gauss' Law (Chapters 21, 22, 23)

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