Q: Which of the following is the value of the elementary charge $$e$$?

$$1.6 \times 10$$^{-19}$$ \ C$$

Question 1

Which of the following statements best describes the conservation of electric charge in a closed system?

Accepted Answer

The net electric charge of a closed system remains constant over time.

Question 2

A glass rod is rubbed with silk and becomes positively charged. What is the correct explanation for this phenomenon?

Accepted Answer

The glass rod loses electrons to the silk.

Question 3

Which of the following is NOT a method of charging an object?

Accepted Answer

Radiation

Question 4

According to Coulomb’s Law, what happens to the force between two point charges if the distance between them is doubled?

Accepted Answer

The force becomes one-fourth as great.

Question 5

Which of the following best describes the difference between conductors and insulators?

Accepted Answer

Conductors allow electric charge to move freely, while insulators do not.

Question 6

A student rubs a plastic rod with fur, and the rod becomes negatively charged. What has happened at the atomic level?

Accepted Answer

The rod has gained electrons from the fur.

Question 7

Which of the following is the correct formula for Coulomb’s Law in SI units?

Accepted Answer

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

Question 8

If two point charges of $$+2 \ \mu C$$ and $$-2 \ \mu C$$ are placed 0.5 m apart in vacuum, what is the magnitude of the force between them? (Use $$k = 8.99 	imes 10^9$ \ N \cdot m^2$/C^2$)

Accepted Answer

$$F = 1.44 	imes 10^2$ \ N$$

Question 9

Which of the following statements about the four fundamental forces is correct?

Accepted Answer

The weak force is responsible for certain types of radioactive decay.

Question 10

A neutral atom becomes a positive ion when:

Accepted Answer

It loses electrons.

Question 11

Which of the following is the value of the elementary charge $$e$$?

Accepted Answer

$$1.6 	imes 10$$^{-19}$$ \ C$$

Question 12

Which of the following best explains why protons do not fly apart in the nucleus despite their positive charges?

Accepted Answer

The strong nuclear force overcomes the electrostatic repulsion at short distances.

Question 13

A metal sphere is charged by induction using a negatively charged rod. What is the final charge on the sphere if it is grounded during the process?

Accepted Answer

The sphere becomes positively charged.

Question 14

Which of the following is a correct statement about the quantization of electric charge?

Accepted Answer

Charge is always a multiple of the elementary charge $$e.$$

Question 15

A student calculates the force between two charges using the wrong distance unit (cm instead of m). If the actual distance is 10 cm, but the student uses 10 in the formula, how will the calculated force compare to the correct value?

Accepted Answer

The calculated force will be 100 times too large.

Question 16

Which of the following is a real-world application of the electromagnetic force?

Accepted Answer

Holding electrons in orbit around the nucleus.

Question 17

If a hydrogen atom has a diameter of approximately $$10^{-10}$$ \ m$$, what is the order of magnitude of its radius?

Accepted Answer

$$10^{-10}$$ \ m$$ divided by 2, so 5$$ 	imes $$10^{-11}$$ \ m$$ (order of magnitude 10$$^{-11}$$ \ m)$$

Question 18

A charged rod is brought near, but does not touch, a neutral metal can on an insulated stand. The can is observed to move toward the rod. What is the best explanation for this behavior?

Accepted Answer

The can is attracted due to induced charges on its surface.

Question 19

Which of the following is the correct value for the Coulomb constant $$k in SI $$units?

Accepted Answer

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

Question 20

A student wants to calculate the electrostatic force between two charges in water, which has a dielectric constant $$\varepsilon_r \u003e 1. $$Compared to the force in vacuum, the force in water will be:

Accepted Answer

Smaller, because the dielectric constant reduces the force.

Physics 212 Fall 2025: Electric Charge and Electric Field Study Notes

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