Currents and Circuits

If a quantity you calculated has units of A • s, what is that quantity?

• potential

• resistivity

• resistance

• charge

For the graph shown in the figure, what physical quantity does the slope of the graph represent for ohmic material?

• power

• resistivity

• resistance

• 1/(resistance)

The length of a certain wire is kept same while its radius is doubled. What is the new resistance of this wire?

• It is increased by a factor of 2.

• It is increased by a factor of 4.

• It is reduced by a factor of 2.

• It is reduced by a factor of 4.

The length of a certain wire is doubled while its radius is kept constant. What is the new resistance of this wire?

• It is 2 times as large.

• It is 3 times as large.

• It is 4 times as large.

• It is 1/2 as large.

Consider two copper wires of equal cross-sectional area. One wire has 3 times the length of the other. How do the resistivities of these two wires compare?

• Both wires have the same resistivity.

• The longer wire has 3 times the resistivity of the shorter wire.

• The longer wire has 9 times times the resistivity of the shorter wire.

• The longer wire has 27 times times the resistivity of the shorter wire.

When the current through a resistor is increased by a factor of 4, the power dissipated by the resistor

• decreases by a factor of 4.

• decreases by a factor of 16.

• increases by a factor of 16.

• increases by a factor of 2.

Over ordinary temperature ranges, the resistance of most metals such as copper

• is independent of the temperature of the metal.

• decreases as the metal gets hotter.

• increases as the metal gets hotter.

• is a maximum at 20°C.

If a charge of 12 C passes through a computer in 2 min, what is the average current through the computer?

• 24 A

• 6 A

• 0.1 A

• 10 A

A current of 1.6 A flows through an electrical device for 10 seconds. How many electrons flow through this device during this time? (e = 1.60 × 10^-19 C)

• 1

• 16

• 1.0×10²⁰

• 1.0×10¹⁹

What potential difference is required across an 8.0-Ω resistor to cause 2.0 A to flow through it?

• 4.0 V

• 16 V

• 32 V

• 128 V