Question 1

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

Accepted Answer

The algebraic sum of all electric charges in any closed system is constant; charge can neither be created nor destroyed, only transferred.

Question 2

A glass rod is rubbed with silk and then brought near a neutral pith ball. The pith ball is attracted to the rod. Which phenomenon explains this attraction?

Accepted Answer

The pith ball is attracted due to polarization, where charges within the neutral object rearrange.

Question 3

Which of the following materials is an example of a conductor?

Accepted Answer

Copper

Question 4

Two identical metal spheres, one with a charge of $$+6\ \mathrm{nC}$$ and the other with $$-2\ \mathrm{nC}$$, are brought into contact and then separated. What is the final charge on each sphere?

Accepted Answer

$$+2\ \mathrm{nC}$$

Question 5

Which equation correctly expresses Coulomb’s Law for the magnitude of the electric 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 6

A point charge $$+Q$$ creates an electric field. At a distance $$r$$ from the charge, what is the magnitude and direction of the electric field?

Accepted Answer

$$E = k \frac{Q}{r^2$}$$, directed away from the charge

Question 7

Which of the following statements about electric field lines is correct?

Accepted Answer

Electric field lines point away from positive charges and toward negative charges.

Question 8

A parallel-plate capacitor has plates of area $$A$$ and charge $$Q on $$each plate. What is the magnitude of the electric field between the plates (neglecting edge effects)?

Accepted Answer

$$E = \frac{Q}{\$$varepsilon_0$$ A}$$

Question 9

If a charged conductor is in electrostatic equilibrium, which of the following is true?

Accepted Answer

The electric field inside the conductor is zero.

Question 10

A small negative test charge is placed in the electric field of a positive point charge. In which direction does the force on the test charge point?

Accepted Answer

Toward the positive charge

Question 11

Which of the following best describes the behavior of excess charge on a conductor?

Accepted Answer

It resides entirely on the surface of the conductor.

Question 12

A DNA fragment with a net negative charge is placed in a gel electrophoresis apparatus with an electric field directed from left to right. In which direction will the DNA fragment move?

Accepted Answer

To the right, toward the positive electrode

Question 13

Which of the following statements about electric dipoles is correct?

Accepted Answer

An electric dipole consists of two charges of equal magnitude and opposite sign separated by a distance.

Question 14

A charged rod is brought near, but does not touch, a neutral metal sphere. What happens to the charges in the sphere?

Accepted Answer

Charges in the sphere rearrange, with opposite charges attracted toward the rod and like charges repelled away.

Question 15

Which of the following is a correct statement about the electric field due to multiple point charges?

Accepted Answer

The net electric field at a point is the vector sum of the fields due to each charge.

Question 16

A lightning rod is designed with a sharp point. Why does this reduce the likelihood of a lightning strike?

Accepted Answer

The sharp point increases the electric field strength, causing ionization of air and allowing excess charge to dissipate safely.

Question 17

Which of the following best describes the direction of the force on a positive charge placed in an electric field?

Accepted Answer

In the same direction as the electric field

Question 18

A neutral atom becomes a positive ion when:

Accepted Answer

It loses an electron.

Question 19

Which of the following is the correct SI unit for electric charge?

Accepted Answer

Coulomb

Question 20

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

Accepted Answer

It becomes one-fourth as large.

Electric Forces and Electric Fields: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards