Question 1

Which of the following statements best describes the Law of Conservation of Charge?

Accepted Answer

Charge can neither be created nor destroyed, only transferred from one object to another.

Question 2

A glass rod is rubbed with silk, causing the rod to become positively charged. Which process is responsible for this?

Accepted Answer

Friction

Question 3

Which of the following materials is a good conductor of electricity and why?

Accepted Answer

Copper, because it has free valence electrons.

Question 4

Two point charges, $$Q_1 = +2$$ \ \mu C$$ and Q_2$ = -2 \ \mu C$$, are separated by a distance $$r. $$According to Coulomb’s Law, what is the direction of the force on $$Q_1$$ due to $$Q_2$$?

Accepted Answer

Toward $$Q_2$$, because opposite charges attract.

Question 5

What is the magnitude of the electric field at a distance $$r$$ from a point charge $$Q$$?

Accepted Answer

$$E = \dfrac{kQ}{r^2$}$$

Question 6

A charged particle of mass $$m$$ and charge $$q is $$placed in a uniform electric field $$E. $$What is its acceleration?

Accepted Answer

$$a = \dfrac{qE}{m}$$

Question 7

Which of the following is NOT a property of electric field lines?

Accepted Answer

They form closed loops around conductors.

Question 8

A thin rod of length $$\ell$$ carries a total charge $$Q$$ distributed uniformly along its length. What is the expression for the electric field at a point on the axis of the rod, a distance $$x$$ from one end?

Accepted Answer

$$E(x) = \dfrac{kQ}{x(x+\ell)}$$

Question 9

A dipole consists of charges $$+e$$ and $$-e$$ separated by a distance $$d. $$What is the dipole moment $$p$$?

Accepted Answer

$$p = ed$$

Question 10

What is the torque $$	au on an $$electric dipole of moment $$p in a $$uniform electric field $$E$$ when the dipole makes an angle $$	heta$$ with the field?

Accepted Answer

$$	au = pE \sin 	heta$$

Question 11

Which of the following best explains why the electric field inside a conductor is zero in electrostatic equilibrium?

Accepted Answer

The charges redistribute themselves on the surface to cancel any internal field.

Question 12

A point charge $$Q is $$placed near a neutral conductor. What happens to the charges in the conductor?

Accepted Answer

They redistribute, with opposite charges attracted toward $$Q$$ and like charges repelled.

Question 13

A charged particle moves in a uniform electric field. Which of the following best describes its motion?

Accepted Answer

It accelerates in the direction of the electric field if positively charged.

Question 14

Which of the following is the correct expression for the force between two point charges $$Q_1$$ and $$Q_2$$ separated by a distance $$r$$?

Accepted Answer

$$F = k \dfrac{Q_1$ Q_2$}{r^2$}$$

Question 15

A parallel plate capacitor is made using two large conducting plates. What is the direction of the electric field between the plates?

Accepted Answer

From the positive plate to the negative plate.

Question 16

A point charge $$Q is $$placed at the center of a spherical conducting shell. What is the electric field inside the conductor (but outside the center)?

Accepted Answer

Zero, because the field inside a conductor is always zero.

Question 17

A charged electroscope is brought near a negatively charged rod. What happens to the leaves of the electroscope?

Accepted Answer

They spread further apart.

Question 18

Which of the following best describes the effect of a Faraday cage?

Accepted Answer

It shields the interior from external electric fields.

Question 19

A surface has a uniform charge density $$\sigma. $$What is the SI unit of $$\sigma$$?

Accepted Answer

$$C/m^2$$

Question 20

Which of the following is a real-world application of electric dipoles?

Accepted Answer

Water molecules aligning in an electric field.

Step-by-Step Guidance for Physics 102: Electric Charges and Electric Fields Problems

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