Question 1

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

Accepted Answer

Electric charge can be moved around, but the total charge in a closed system remains constant.

Question 2

A plastic rod is rubbed with fur and then brought near small pieces of paper. The paper is attracted to the rod. What is the best explanation for this phenomenon?

Accepted Answer

The rod induces a net positive charge on the side of the paper facing it, causing attraction.

Question 3

Which equation correctly expresses the magnitude of the electrostatic 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 4

Two identical small spheres are suspended by insulating threads. Sphere A has a charge of $$+Q$$ and sphere B has a charge of $$-Q. $$What will happen when they are brought close together?

Accepted Answer

They will attract each other.

Question 5

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

Accepted Answer

Negative charges in the neutral ball are attracted toward the positively charged ball, causing an induced negative charge on the near side.

Question 6

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

Accepted Answer

Copper

Question 7

Three charges are fixed in a line: $$+2q$$, $$-q$$, and $$+q. $$Which charge experiences the largest magnitude of force?

Accepted Answer

The central charge ($$-q)$$

Question 8

A charged sphere with $$Q = +60 \mu C is $$suspended by a silk thread in a uniform upward electric field of $$E = 3000 	ext{ N/C}. If $$the mass of the sphere is $$0.05 	ext{ kg}$$, what is the tension in the thread?

Accepted Answer

$$2.07 	ext{ N}$$

Question 9

Which of the following best describes the direction of the electric field produced by a positive point charge?

Accepted Answer

Radially outward from the charge

Question 10

A test charge $$q is $$placed in an electric field $$E. $$What is the force $$F$$ experienced by the charge?

Accepted Answer

$$F = qE$$

Question 11

Two charges, $$Q_1 = -10$$ \mu C$$ and Q_2$, are separated by 1.40$$ 	ext{ m}$$. The electric field is zero at a point 0.40$$ 	ext{ m}$$ from Q_1$ along the line joining the charges. What is the value of Q_2$?

Accepted Answer

$$Q_2 = +25$$ \mu C$$

Question 12

Which of the following field patterns could represent a possible electrostatic field in a region with no charges?

Accepted Answer

Field lines that begin and end on charges outside the region

Question 13

A negatively charged comb is brought near small pieces of paper. What happens to the electrons in the paper molecules?

Accepted Answer

They are repelled, creating an induced positive charge on the side facing the comb.

Question 14

A charged particle is fired into a region between two large parallel plates with a uniform electric field directed upward. Which path will the particle follow if it is negatively charged?

Accepted Answer

It will curve downward.

Question 15

If the charge on each of two repelling balls suspended in a test tube is doubled, what happens to the distance between the balls?

Accepted Answer

It increases by a factor of $$\sqrt{2}.$$

Question 16

Which of the following statements about electric field lines is correct?

Accepted Answer

The density of field lines indicates the strength of the electric field.

Question 17

A positive test charge is placed at the center of two fixed charges: $$-2.4 	ext{ nC} to $$the left and $$-1.2 	ext{ nC} to $$the right. What is the direction of the net force on the test charge?

Accepted Answer

To the left

Question 18

An electron escapes from the negative plate of a capacitor producing a uniform electric field of $$2.00 	imes 10^4$ 	ext{ N/C}. $$Starting from rest, the electron takes $$2.00 	imes 10$$^{-6}$$ seconds to travel to the positive plate. How far apart are the plates?

Accepted Answer

$$2.28 	ext{ cm}$$

Question 19

Which of the following is the SI unit of electric charge?

Accepted Answer

Coulomb

Electric Charges, Forces, and Fields: Study Notes

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