Chapter 17: Current and Resistance

Question 1

A resistor, R, is made out of a particular material with resistivity ρ. The cylindrically shaped resistor has a length of L and radius r. To get four times as much resistance in your resistor you could
Select one:
a. make the radius half as big. 
b. make the radius one quarter the size.
c. make the radius four times as big.
d. make the radius twice as big.

Answer 1

make the radius half as big.

Question 2

Electrons flow through a circuit in the clockwise direction. The current is traveling
Select one:
a. in a direction impossible to tell without knowing what the positive charges are doing.
b. counterclockwise.
c. clockwise.
d. not at all.

Answer 2

counterclockwise

Question 3

Suppose a current-carrying wire has a cross-sectional area that gradually becomes smaller along the wire so that the wire has the shape of a very long, truncated cone. How does the drift speed vary along the wire?
Select one:
a. It slows down as the cross section becomes smaller.
b. It speeds up as the cross section becomes smaller.
c. More information is needed.
d. It doesn’t change.

Answer 3

It speeds up as the cross section becomes smaller.

Question 4

Suppose an electrical wire is replaced with one having every linear dimension doubled (i.e., the length and radius have twice their original values). The wire now has
Select one:
a. more resistance than before.
b. less resistance.
c. The same resistance.

Answer 4

less resistance.

Question 5

The battery powering a light bulb is disconnected. As the light bulb’s heat dissipates, how will the resistance and current change?
Select one:
a. The resistance will increase and the current will be zero.
b. The resistance will decrease and the current will be zero.
c. The resistance will decrease and the current will increase.
d. The resistance will increase and the current will decrease.

Answer 5

The resistance will decrease and the current will be zero.

Question 6

Two resistors, A and B, are connected in a series circuit with a battery. The resistance of A is twice that of B. Which resistor dissipates more power?
Select one:
a. Resistor B does.
b. More information is needed.
c. Resistor A does.

Answer 6

Resistor A does

Question 7

Which of the following best describes the inner workings of conductors?
Select one:
a. The electrons start at one electrode and travel directly to the other electrode, stopping there.
b. None of these choices is correct.
c. Electrons collide at random, experiencing a net change of position equal to zero, except when exposed to an external electric field.
d. The electrons’ drift speed depends only on the material of the conductor and not on the voltage difference applied to it.

Answer 7

Electrons collide at random, experiencing a net change of position equal to zero, except when exposed to an external electric field.