Question 1

Which of the following statements about electric charge is correct?

Accepted Answer

Electric charge is quantized and conserved.

Question 2

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 3

Which equation correctly represents Coulomb's Law for the force between two charges $$q_1$$ and $$q_2$$ separated by distance $$r in $$vacuum?

Accepted Answer

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

Question 4

A plastic rod is rubbed with wool and becomes negatively charged. What is the best explanation for this phenomenon?

Accepted Answer

Electrons are transferred from the wool to the rod.

Question 5

Which of the following is NOT a possible effect produced by electric charge?

Accepted Answer

It can produce gravitational waves.

Question 6

What is the formula for the electric field $$E$$ due to a point charge $$q at a $$distance $$r in $$vacuum?

Accepted Answer

$$E = k \frac{q}{r^2$}$$

Question 7

A dipole of moment $$p is $$placed in a uniform electric field $$E. $$What is the expression for the torque $$	au$$ acting on the dipole?

Accepted Answer

$$	au = pE \sin 	heta$$

Question 8

Which of the following best describes the dielectric constant $$K$$?

Accepted Answer

It is the ratio of the permittivity of the medium to the permittivity of free space.

Question 9

According to Gauss's Law, the total electric flux $$\Phi$$ through a closed surface is proportional to:

Accepted Answer

The total charge enclosed by the surface.

Question 10

Which of the following is the correct mathematical statement of Gauss's Law?

Accepted Answer

$$\Phi = \oint \vec{E} \cdot d\vec{A} = \frac{q_{encl}}{\$$varepsilon_0$$}$$

Question 11

A conducting sphere of radius $$R$$ carries a charge $$Q. $$What is the electric field just outside its surface?

Accepted Answer

$$E = \frac{Q}{4\pi \$$varepsilon_0$$ R^2$}$$

Question 12

Which of the following is a correct application of Gauss's Law for an infinite plane sheet of charge with surface charge density $$\sigma$$?

Accepted Answer

$$E = \frac{\sigma}{2\$$varepsilon_0$$}$$

Question 13

Which of the following is NOT a type of charge distribution?

Accepted Answer

Thermal charge distribution

Question 14

If the electric flux through a closed surface is zero, which of the following must be true?

Accepted Answer

There is no charge inside the surface.

Question 15

A dipole is placed in a uniform electric field. In which orientation is the dipole in stable equilibrium?

Accepted Answer

When the dipole moment is parallel to the electric field.

Question 16

Which of the following best describes the electric flux $$\Phi$$ through a surface?

Accepted Answer

It is a measure of the number of electric field lines passing through the surface.

Question 17

Which of the following is the correct formula for the electric field inside a uniformly charged shell (using Gauss's Law)?

Accepted Answer

$$E = 0$$

Question 18

Which of the following is the correct expression for the dipole moment $$p of an $$electric dipole?

Accepted Answer

$$p = q 	imes 2a$$

Question 19

A dielectric material is inserted between the plates of a parallel plate capacitor. What happens to the capacitance?

Accepted Answer

The capacitance increases by a factor equal to the dielectric constant.

Electric Charges and Fields: Core Concepts and Laws

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