Question 1

Which of the following statements best describes the process of charging by friction?

Accepted Answer

It involves transferring electrons between objects, resulting in one object gaining electrons and the other losing electrons.

Question 2

A glass rod rubbed with silk becomes positively charged. What is the best explanation for this observation?

Accepted Answer

Electrons are transferred from the glass rod to the silk.

Question 3

Which equation correctly expresses the quantization of charge for a macroscopic object?

Accepted Answer

$$q = (N_p - N_e) e$$

Question 4

A neutral atom becomes a positive ion by:

Accepted Answer

Losing an electron.

Question 5

In the experiment where a charged plastic rod touches a neutral metal sphere, what happens to the sphere?

Accepted Answer

It acquires a charge and can pick up small pieces of paper.

Question 6

Which material allows charge to move freely through it?

Accepted Answer

Metal

Question 7

What is the main difference between conductors and insulators?

Accepted Answer

Conductors allow electrons to move freely, while insulators do not.

Question 8

A positively charged rod is brought near a neutral piece of metal. What force acts on the metal?

Accepted Answer

An attractive polarization force.

Question 9

Which of the following best describes an electric dipole?

Accepted Answer

A pair of equal and opposite charges separated by a distance.

Question 10

Two identical metal spheres are initially neutral and touching. A charged rod is brought near, then removed, and the spheres are separated. What are the final charges on the spheres?

Accepted Answer

$$Q_1 is 0 $$and $$Q_2 is 0.$$

Question 11

Which equation represents Coulomb's Law for the magnitude of the force between two point charges?

Accepted Answer

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

Question 12

If two charges $$q_1$$ and $$q_2$$ are separated by a distance $$r$$, and $$q_1 is $$positive while $$q_2 is $$negative, what is the direction of the force on $$q_1$$?

Accepted Answer

Toward $$q_2.$$

Question 13

A small glass bead of mass $$15 mg $$and charge $$+10 nC is at $$rest on a table. A plastic sphere with charge $$-10 nC is $$held $$1.0 cm $$above it. Will the bead leap up to the sphere? (Assume $$K = 8.99 	imes 10^9$ N m^2$/C^2$ and g = 9.8$ m/s^2$)

Accepted Answer

Yes, because the electric force exceeds the gravitational force.

Question 14

Three charges $$q_1 = -50$ nC, q_2$ = +50 nC$$, and $$q_3 = +30$ nC are placed at the corners of a 5.0$ cm $$	imes$$ 10.0$ cm rectangle. What is the net force on q_3$ due to the other two charges?

Accepted Answer

The net force is the vector sum of the forces from $$q_1$$ and $$q_2$$, calculated using $$F = \frac{K |q_1$||q_3$|}{r^2$}$$ and $$F = \frac{K |q_2$||q_3$|}{r^2$}.$$

Question 15

Which of the following best describes the concept of an electric field?

Accepted Answer

A function that assigns a vector to every point in space, representing the force per unit charge.

Question 16

What are the units of the electric field strength $$E$$?

Accepted Answer

Newtons per Coulomb (N/C)

Question 17

Using unit vector notation, what is the electric field at a distance $$r$$ from a point charge $$q$$?

Accepted Answer

$$\vec{E} = \frac{K q}{r^2$} \hat{r}$$

Question 18

What is the electric field strength at the position of the electron in a hydrogen atom, given the proton is at the center and the electron orbits at a radius of $$0.053 nm$$? ($$e = 1.6 	imes 10$$^{-19}$$ C, K = 8.99$$ 	imes $$10^9 N m$^2/C$^2)$$

Accepted Answer

$$E = \frac{K e}{r^2$}$$

Study Notes: Chapter 22 – Electric Charges and Forces

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