Question 1

In the first image, a person rubs their hair on a couch and experiences a static shock. Which physical process best explains why this happens?

Accepted Answer

The friction transfers electrons from the couch to the person, charging them by friction.

Question 2

Which law describes the force between two point charges and what is its mathematical form?

Accepted Answer

Coulomb's Law: $$F = k \frac{|q_1$ q_2$|}{r^2$}$$

Question 3

A plastic rod is rubbed with wool and then brought near small pieces of paper. The paper jumps to the rod. What is the best explanation?

Accepted Answer

The rod becomes negatively charged and polarizes the paper, causing attraction.

Question 4

Which of the following statements about conductors and insulators is correct?

Accepted Answer

In conductors, electrons are free to move; in insulators, electrons are tightly bound.

Question 5

A neutral metal sphere is touched by a negatively charged rod. What happens to the sphere?

Accepted Answer

It gains electrons and becomes negatively charged.

Question 6

Which experiment demonstrates that charge is quantized?

Accepted Answer

Objects always have charges that are integer multiples of $$e.$$

Question 7

A glass rod rubbed with silk is brought near a hanging plastic rod rubbed with wool. What is observed and why?

Accepted Answer

They attract because they have opposite types of charge.

Question 8

Which of the following best describes the electric field at a point in space?

Accepted Answer

It is the force per unit charge that a positive test charge would experience at that point.

Question 9

A singly charged calcium ion ($$q = +e) is in a $$cell membrane electric field of $$1.0 	imes 10^7$ N/C. What is the magnitude of the electric force on the ion? (e = 1.6$$ 	imes $$10^{-19} C)$$

Accepted Answer

$$1.6 	imes 10$$^{-12}$$ N

Question 10

Which of the following is true about the force between two protons in a helium nucleus?

Accepted Answer

The electric repulsive force is much greater than the gravitational attractive force.

Question 11

What is the effect of bringing a charged rod near a neutral metal object without touching it?

Accepted Answer

The metal object becomes polarized, with opposite charges accumulating near the rod.

Question 12

Which of the following best describes charging by induction?

Accepted Answer

A neutral conductor is charged without direct contact by separating charges using a nearby charged object.

Question 13

If two identical metal spheres, both initially neutral, are touched together and a charged rod is brought near, then the spheres are separated and the rod is removed, what is the result?

Accepted Answer

The spheres have equal and opposite charges.

Question 14

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

Accepted Answer

$$E = \frac{1}{4\pi \$$epsilon_0$$} \frac{|q|}{r^2$}$$

Question 15

A proton and an electron are separated by a distance $$r. $$What is the direction of the electric field at the position of the electron due to the proton?

Accepted Answer

Toward the proton

Question 16

Which of the following is true about the unit vector $$\hat{r}$$ used in electric field equations?

Accepted Answer

It has no units and only indicates direction.

Question 17

Why do neutral objects get attracted to charged objects?

Accepted Answer

Because of charge polarization, which induces opposite charges on the near side.

Question 18

Which constant is used in Coulomb’s law and what is its value in SI units?

Accepted Answer

$$k = 8.99 	imes 10^9$ N m^2$/C^2$

Question 19

Which of the following is a real-world application of electric charge and force?

Accepted Answer

Nerve signal propagation in cell membranes due to electric fields.

Ch. 22 Electric Charges and Forces: Study Notes for Physics College Students

Study Guide - Practice Questions

Study Guide - Flashcards