Question 1

Which of the following statements best describes the law of conservation of electric charge?

Accepted Answer

The net amount of electric charge produced in any process is zero.

Question 2

A neutral atom becomes a positive ion when:

Accepted Answer

It loses one or more electrons.

Question 3

Which of the following is the correct expression for the magnitude of the electrostatic force between two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r$$?

Accepted Answer

$$F = k \frac{q_1$ q_2$}{r^2$}$$

Question 4

A metal sphere is charged by induction using a negatively charged balloon. After grounding and removing the balloon, what is the net charge on the sphere?

Accepted Answer

Positive

Question 5

Which of the following best explains why metals are good conductors of electricity?

Accepted Answer

Their valence electrons are free to move throughout the solid.

Question 6

A charged balloon is brought near a neutral wall and sticks to it. What is the best explanation for this phenomenon?

Accepted Answer

The charges in the wall redistribute, causing attraction by induction.

Question 7

If the distance between two point charges is doubled, what happens to the magnitude of the electrostatic force between them?

Accepted Answer

It becomes one-fourth as large.

Question 8

Which of the following is the correct formula for the electric field $$E$$ due to a point charge $$q at a $$distance $$r$$?

Accepted Answer

$$E = k \frac{q}{r^2$}$$

Question 9

A proton and an electron are placed in a uniform electric field pointing to the right. Which statement is correct about their accelerations?

Accepted Answer

They accelerate in opposite directions; the proton to the right and the electron to the left.

Question 10

A dipole with dipole moment $$p is $$placed in a uniform electric field $$E at an $$angle $$\phi to $$the field. What is the torque $$	au on $$the dipole?

Accepted Answer

$$	au = pE \sin \phi$$

Question 11

What is the potential energy $$U of an $$electric dipole in a uniform electric field $$E at an $$angle $$\phi$$?

Accepted Answer

$$U = -pE \cos \phi$$

Question 12

A small neutral object is brought near a negatively charged rod. What happens?

Accepted Answer

The neutral object is attracted to the rod due to induced polarization.

Question 13

Which of the following is true about the quantization of electric charge?

Accepted Answer

The charge of any object is always an integer multiple of $$e = 1.6 	imes 10$$^{-19}$$ C.

Question 14

A charged particle of mass $$m$$ and charge $$q$$ enters a region with a uniform electric field $$E$$ perpendicular to its initial velocity $$v_0. $$What is the shape of its trajectory?

Accepted Answer

A parabola

Question 15

Which of the following best describes the direction of the electric field created by a positive point charge?

Accepted Answer

Radially outward from the charge

Question 16

If the charge on both objects in Coulomb’s law is doubled and the distance between them is also doubled, what happens to the force?

Accepted Answer

It remains the same.

Question 17

Which of the following is the correct unit for the electric field?

Accepted Answer

$$\mathrm{N/C}$$

Question 18

A water molecule is an example of:

Accepted Answer

An electric dipole

Question 19

Which of the following is the correct vector equation for the torque $$\vec{	au} on a $$dipole in an electric field $$\vec{E}$$?

Accepted Answer

$$\vec{	au} = \vec{p} 	imes \vec{E}$$

Electric Charges and Forces: Foundations of Electrostatics

Study Guide - Practice Questions

Study Guide - Flashcards