Question 1

Which of the following statements best explains why two glass rods rubbed with silk repel each other, as shown in the first image?

Accepted Answer

Both rods acquire a positive charge, and like charges repel.

Question 2

When a plastic rod is rubbed with fur, as shown in the second image, what type of charge does the rod acquire and why?

Accepted Answer

Negative, because electrons are transferred from the fur to the rod.

Question 3

In the third image, a plastic rod rubbed with fur is brought near a glass rod rubbed with silk. The rods attract each other. What does this demonstrate about the nature of electric charge?

Accepted Answer

Unlike charges attract each other.

Question 4

Which experiment led to the conclusion that electric charge is quantized and always occurs in integer multiples of a fundamental value?

Accepted Answer

Millikan oil-drop experiment

Question 5

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

Accepted Answer

Electrons in the sphere are repelled, causing the near side to become positively charged and the far side negatively charged.

Question 6

Which of the following best describes the process of charging by induction?

Accepted Answer

A charged object is brought near a conductor, causing a redistribution of charges without direct contact.

Question 7

Which of the following equations correctly expresses Coulomb's Law for the magnitude of the force between two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r$$?

Accepted Answer

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

Question 8

A metal sphere is charged by contact with a negatively charged rod. What is the sign of the charge left on the sphere after the rod is removed?

Accepted Answer

Negative, because electrons are transferred from the rod to the sphere.

Question 9

Which of the following statements about conductors in electrostatic equilibrium is FALSE?

Accepted Answer

The electric field inside the conductor is nonzero.

Question 10

A test charge $$q_0$$ experiences a force $$F at a $$point in space. What is the electric field $$E at $$that point?

Accepted Answer

$$E = \frac{F}{q_0$}$$

Question 11

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

Accepted Answer

Radially outward from the charge.

Question 12

If two point charges $$q_1$$ and $$q_2$$ are separated by a distance $$r$$, and the force between them is $$F$$, what will be the new force if the distance is doubled?

Accepted Answer

$$F/4$$

Question 13

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

Accepted Answer

They never cross each other.

Question 14

A dipole consists of charges $$+q$$ and $$-q$$ separated by a distance $$2a. $$What is the magnitude of its dipole moment $$p$$?

Accepted Answer

$$p = 2aq$$

Question 15

A dipole is placed in a uniform electric field $$E$$ making an angle $$	heta$$ with the field. What is the magnitude of the torque $$	au on $$the dipole?

Accepted Answer

$$	au = pE \sin 	heta$$

Question 16

Which of the following best explains why a charged comb can pick up small pieces of paper?

Accepted Answer

The electric field of the comb polarizes the paper, inducing opposite charges on its near side.

Question 17

Which of the following is TRUE about the comparison between gravitational and electric forces?

Accepted Answer

Electric forces can be both attractive and repulsive, while gravitational forces are always attractive.

Question 18

A conductor is placed in electrostatic equilibrium. Which of the following statements is correct?

Accepted Answer

The electric field inside the conductor is zero.

Question 19

A small test charge $$q_0 is $$placed at a distance $$r$$ from a point charge $$Q. $$What is the magnitude of the electric field at that point?

Accepted Answer

$$E = k_e \frac{Q}{r^2$}$$

Question 20

A negatively charged rod is brought near a neutral insulator. What happens to the charges in the insulator?

Accepted Answer

The charges in the molecules realign, causing polarization.

Electric Charge and Electric Field: Fundamental Concepts and Applications

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