$$e = 1.60 \times 10$$^{-19}$$ coulombs

$$6.25 \times 10$$^{18}$$ protons

$$n = \frac{-3.20 \times 10$$^{-19}$$}{1.60 \times 10$$^{-19}$$} = -2$$ electrons

Question 1

Which of the following statements best describes the Law of Charges?

Accepted Answer

Like charges repel and unlike charges attract.

Question 2

When a rubber balloon is rubbed against hair, what is the resulting charge on the balloon and why?

Accepted Answer

The balloon becomes negatively charged because electrons transfer from hair to balloon.

Question 3

What is the value of the elementary charge $$e$$?

Accepted Answer

$$e = 1.60 	imes 10$$^{-19}$$ coulombs

Question 4

Which of the following is true about protons and electrons?

Accepted Answer

Electrons are elementary particles, protons are not.

Question 5

How many excess protons are required to give an object a net charge of $$1$$ coulomb?

Accepted Answer

$$6.25 	imes 10$$^{18}$$ protons

Question 6

Which equation correctly relates the net charge $$q on an $$object to the number of excess charge carriers $$n$$ and the elementary charge $$e$$?

Accepted Answer

$$q = n e$$

Question 7

A glass rod is rubbed with silk. What is the resulting charge on the glass rod and why?

Accepted Answer

The glass rod becomes positively charged because electrons transfer from glass rod to silk.

Question 8

Which of the following best explains why charge is quantized?

Accepted Answer

Charge is always a multiple of the elementary charge because you cannot have a fraction of an electron or proton.

Question 9

Calculate the number of excess electrons required to give an object a net charge of $$-3.20 	imes 10$$^{-19}$$ C.

Accepted Answer

$$n = \frac{-3.20 	imes 10$$^{-19}$$}{1.60 	imes 10$$^{-19}$$} = -2$$ electrons

Question 10

Which of the following is a correct statement about the composition of a neutron?

Accepted Answer

A neutron is made of one up quark and two down quarks.

Question 11

If a balloon is rubbed against hair and then sticks to a wall, which phenomenon is primarily responsible for this behavior?

Accepted Answer

Polarization of charges in the wall.

Question 12

Which of the following best describes the charge of a proton in terms of quarks?

Accepted Answer

A proton is made of two up quarks and one down quark, giving it a charge of $$+e.$$

Question 13

Which of the following is the correct mass ratio of a proton to an electron?

Accepted Answer

$$\frac{m_{proton}}{m_{electron}} \approx 1830$$

Question 14

A student claims an object can have a net charge of $$-2.00 	imes 10$$^{-19}$$ C. Is this possible? Why or why not?

Accepted Answer

No, because charge must be an integer multiple of the elementary charge.

Question 15

Which of the following real-life scenarios best demonstrates the Law of Charges?

Accepted Answer

Two balloons, both rubbed on hair, repel each other when brought close.

Question 16

If $$q = 4.80 	imes 10$$^{-19}$$ C, how many excess electrons does the object have?

Accepted Answer

$$n = \frac{4.80 	imes 10$$^{-19}$$}{1.60 	imes 10$$^{-19}$$} = 3$$ protons

Electric Charge: Properties, Quantization, and Interactions

Study Guide - Practice Questions