Question 1

Which of the following statements best describes the process of charging by friction, as observed when rubbing amber with wool?

Accepted Answer

One object becomes positively charged and the other negatively charged, depending on their positions in the triboelectric series.

Question 2

A neutral copper sphere is touched by a negatively charged rod and then separated. What is the resulting charge on the copper sphere?

Accepted Answer

It becomes negatively charged.

Question 3

Which of the following best explains why conductors allow electric current to flow easily?

Accepted Answer

They have abundant mobile charge carriers.

Question 4

A glass rod is rubbed with silk, and the rod becomes positively charged. What happens at the atomic level?

Accepted Answer

Electrons are transferred from the rod to the silk.

Question 5

Which equation correctly expresses the quantization of electric charge?

Accepted Answer

$$q = n e$$

Question 6

Two identical isolated conductors have charges $$-2Q$$ and $$-4Q. $$They are briefly put into contact and then separated. What is the final charge on each conductor?

Accepted Answer

Each will have $$-3Q of $$charge.

Question 7

A conducting sphere of radius $$R$$ has a uniform volume charge density $$\rho. $$What is the total charge $$Q in $$the sphere?

Accepted Answer

$$Q = \frac{4}{3} \pi R^3$ \rho$$

Question 8

According to Coulomb's Law, what is the magnitude of the 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 9

A spherical insulator of mass $$8.00 	imes 10$$^{-7}$$ kg and charge 600$$ \mu$$C is hung by a thin wire. A charge q_2$ = -0.900 \muC is $$held $$0.150 m $$away. What additional force acts on the sphere due to the presence of $$q_2$$?

Accepted Answer

An attractive electrostatic force given by $$F = k \frac{|q_1$ q_2$|}{r^2$}$$

Question 10

What is the ratio of the electric force to the gravitational force between a proton and an electron separated by a distance $$r$$?

Accepted Answer

$$\frac{F_{electric}}{F_{gravity}} = \frac{k e^2$}{G m_p m_e}$$

Question 11

A point charge $$q is $$placed at a location where the electric field is $$\vec{E}. $$What is the force $$\vec{F} on $$the charge?

Accepted Answer

$$\vec{F} = q \vec{E}$$

Question 12

What is the direction of the electric field produced by a negative point charge?

Accepted Answer

Radially inward toward the charge.

Question 13

A dipole consists of charges $$+q$$ and $$-q$$ separated by distance $$d. $$What is the magnitude of its dipole moment $$p$$?

Accepted Answer

$$p = qd$$

Question 14

A non-conducting disk of radius $$R$$ has a uniform positive surface charge density $$\sigma. $$What is the electric field at a point along the axis of the disk at a distance $$x$$ from its center (for $$x \u003e 0$$)?

Accepted Answer

Question 15

What is the electric field near a large sheet of charge with surface charge density $$\sigma$$?

Accepted Answer

$$E = \frac{\sigma}{2 \$$epsilon_0$$}$$

Question 16

A dipole is placed in a uniform electric field. What is the torque $$	au$$ experienced by the dipole?

Accepted Answer

$$	au = pE \sin 	heta$$

Question 17

A charged particle of mass $$m$$ and charge $$-q is $$placed at the center of a uniformly charged ring of total charge $$Q$$ and radius $$a. If $$displaced slightly along the axis and released, what type of motion does it undergo?

Accepted Answer

Simple harmonic motion with frequency $$f = \frac{1}{2\pi} \sqrt{\frac{kQq}{ma^3$}}$$

Question 18

Which of the following is a property of electric field lines?

Accepted Answer

They never cross each other.

Question 19

A dipole is initially aligned with a uniform electric field. How much work must be done by an external agent to rotate the dipole by $$180^\circ$$?

Accepted Answer

$$2qEd$$

Electric Charge and Electric Field (Chapter 21) – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards