Question 1

Which statement best describes the law of conservation of charge?

Accepted Answer

Charge is transferred from one place to another, but the net charge remains constant.

Question 2

A glass rod rubbed with silk acquires a positive charge. If it is brought near a plastic rod rubbed with wool (which acquires a negative charge), what type of force will act between them?

Accepted Answer

An attractive force

Question 3

Which equation correctly represents Coulomb’s law for the magnitude of the force between two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r$$?

Accepted Answer

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

Question 4

A neutral sphere is brought near a positively charged rod. What happens to the charges in the sphere?

Accepted Answer

Negative charges in the sphere are attracted to the rod, causing polarization.

Question 5

Which material is an insulator?

Accepted Answer

Glass

Question 6

If two identical metal spheres, initially neutral, are touched together and then separated after a charged rod is brought near, what is the resulting charge on the spheres?

Accepted Answer

One sphere is positive and the other is negative.

Question 7

What is the SI unit for electric charge?

Accepted Answer

Coulomb (C)

Question 8

A small glass bead with mass $$15\,	ext{mg}$$ and charge $$+10\,	ext{nC} is $$placed $$1.0\,	ext{cm}$$ below a plastic sphere with charge $$-10\,	ext{nC}. $$Will the bead leap upward? (Assume $$K = 9.0 	imes 10^9$\,	ext{N}\cdot	ext{m}^2/	ext{C}^2$$ and $$g = 9.8\,	ext{m}/	ext{s}^2)$$

Accepted Answer

Yes, the electric force is greater than the weight.

Question 9

Which statement about conductors in electrostatic equilibrium is correct?

Accepted Answer

The electric field inside the conductor is zero.

Question 10

What is the direction of the electric field at the surface of a charged conductor?

Accepted Answer

Perpendicular to the surface

Question 11

A dipole is placed in a uniform electric field. What happens when it is released from rest?

Accepted Answer

It rotates to align its dipole moment with the field.

Question 12

What is the electric field at a point due to multiple charges?

Accepted Answer

The vector sum of the fields from each charge.

Question 13

Which equation gives the force on a charge $$q in a $$known electric field $$\vec{E}$$?

Accepted Answer

$$\vec{F} = q \vec{E}$$

Question 14

A positively charged particle is placed in an electric field. In which direction does the force act?

Accepted Answer

In the direction of the electric field

Question 15

Which of the following best describes the electric field lines for a dipole?

Accepted Answer

Lines start on positive charges and end on negative charges.

Question 16

In gel electrophoresis, why do DNA fragments move through the gel?

Accepted Answer

Because they have a negative charge and are pulled by the electric field.

Question 17

A proton in a hydrogen atom orbits at a radius of $$0.053\,	ext{nm}. $$What is the electric field at the position of the electron due to the proton? (Use $$K = 9.0 	imes 10^9$\,	ext{N}\cdot	ext{m}^2/	ext{C}^2$$, $$e = 1.60 	imes 10$$^{-19}$$\,	ext{C})$$

Accepted Answer

$$E = 5.1 	imes 10$$^{11}$$\,	ext{N}/	ext{C}$$

Question 18

Which point near a positive charge has the strongest electric field?

Accepted Answer

A point closer to the charge

Question 19

What is the effect of a conducting enclosure (such as a metal box) on the electric field inside it?

Accepted Answer

The electric field inside is zero.

Chapter 20: Electric Fields and Forces – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards