Q: Which of the following is the value of the electric constant (permittivity of free space) $\epsilon_0$?

$8.85 \times 10^{-12} \text{ C}^2/\text{N} \cdot \text{m}^2$

Question 1

Which of the following statements best describes the law of conservation of electric charge?

Accepted Answer

The total electric charge in a closed system remains constant over time.

Question 2

According to Coulomb's Law, what is the magnitude of the force between two point charges $q_1$ and $q_2$ separated by a distance $r$?

Accepted Answer

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

Question 3

A person shuffles across a carpet and accumulates a net charge of $1 	ext{ nC}$. How many elementary charges ($e = 1.602 	imes 10^{-19} 	ext{ C}$) does this correspond to?

Accepted Answer

$6.24 	imes 10^9$

Question 4

Which of the following best explains why charge on a conductor redistributes itself when placed in an electric field?

Accepted Answer

Because conductors have free electrons that move to cancel the internal electric field.

Question 5

If four identical charges $q$ are placed at the corners of a square of side $a$, what is the net force on a charge $+q$ placed at the center of the square?

Accepted Answer

Zero, because the forces from the four corner charges cancel by symmetry.

Question 6

Which of the following is a correct statement about polarization in metals?

Accepted Answer

Polarization in metals involves the rearrangement of free electrons in response to an external charge.

Question 7

A negatively charged rod is brought near an uncharged metal ball supported on an insulating stand. What happens to the charges in the ball?

Accepted Answer

Free electrons in the ball are repelled, causing positive charges to accumulate closer to the rod.

Question 8

Which of the following is the value of the electric constant (permittivity of free space) $\epsilon_0$?

Accepted Answer

$8.85 	imes 10^{-12} 	ext{ C}^2/	ext{N} \cdot 	ext{m}^2$

Question 9

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

Accepted Answer

Conductors allow free movement of charge, while insulators keep charge fixed in place.

Question 10

Two point charges, $q_1 = +2 	ext{ nC}$ and $q_2 = -3 	ext{ nC}$, are separated by $0.5 	ext{ m}$. What is the direction of the force on $q_1$ due to $q_2$?

Accepted Answer

Toward $q_2$, because the charges are opposite and attract.

Question 11

A charge $q_1$ is located at $(2, 3)$ meters and $q_2$ at $(5, 7)$ meters. What is the displacement vector $\vec{r}_{12}$ from $q_1$ to $q_2$?

Accepted Answer

$\vec{r}_{12} = 3\hat{i} + 4\hat{j}$

Question 12

Which experiment provided evidence that electric charge is quantized?

Accepted Answer

Millikan oil drop experiment

Question 13

If the force between two charges is $F$ at a distance $r$, what will be the force if the distance is doubled?

Accepted Answer

$F/4$

Question 14

Which of the following is true about the direction of the electric force between two charges?

Accepted Answer

It acts along the line joining the two charges.

Question 15

A $+1 	ext{ nC}$ charge is at $(5, 5)$ m and a $-2 	ext{ nC}$ charge is at $(1, 2)$ m. What is the magnitude of the displacement vector from the $+1 	ext{ nC}$ charge to the $-2 	ext{ nC}$ charge?

Accepted Answer

$5 	ext{ m}$

Question 16

Which of the following is the correct unit for electric charge?

Accepted Answer

Coulomb (C)

Question 17

What is the effect of grounding a conductor?

Accepted Answer

It provides a path for excess charge to flow away, neutralizing the conductor.

Question 18

Which of the following best describes the behavior of charge on an insulator?

Accepted Answer

Charge remains fixed in position once placed on the insulator.

Question 19

If three charges $A$, $B$, and $C$ are such that $A$ attracts $B$, $A$ repels $C$, and $A$ feels no force from $D$, what can be inferred about the forces between $B$, $C$, and $D$?

Accepted Answer

B and C also feel no force from D.

Electric Charge, Coulomb’s Law, Conductors, Insulators, & Polarization – Physics 1200 Lecture 01 Study Notes

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