Question 1

The resistivity of the material of a wire is 1.76 × 10-8 Ω ∙ m. If the diameter of the wire is 2.00 mm and its length is 2.00 m, what is its resistance?

Accepted Answer

A)  112 Ω 
B)  11.2 Ω 
C)  1.12 Ω 
D)  0.112 Ω 
E)  0.0112 Ω

Question 2

How much does it cost to operate a 25-W soldering iron for 8.0 hours if energy costs 8.0¢/kWh?

Accepted Answer

A)  $1.50 
B)  25¢ 
C)  16¢ 
D)  1.6¢

Question 3

For the graph shown in the figure, what physical quantity does the slope of the graph represent for a dc circuit?

Accepted Answer

A)  1/(current) 
B)  resistance 
C)  1/(resistance) 
D)  current 
E)  resistivity

Question 4

A battery supplies 6.0 mA to a 12-Ω resistor for 1.5 h. How much electric energy does this resistor dissipate in this time?

Accepted Answer

The answer of A battery supplies 6.0 mA to a...

Question 5

A flashlight draws 0.133 A from a 3.0-V battery pack. In 2.0 minutes (a) how much charge flows from the battery, (b) how much energy does the battery supply, and (c) how many electrons have passed any point in the circuit every second?

Accepted Answer

The answer of A flashlight draws 0.133 A from a...

Question 6

During a period of high power demand, the voltage output of the power company is reduced by 5.0%. By what percentage is the power in a resistor decreased?

Accepted Answer

A)  2.5% 
B)  5.0% 
C)  10% 
D)  15% 
E)  90%

Question 7

A 120-Ω laboratory resistor is rated at 0.25 W. How much current can safely flow through the resistor?

Accepted Answer

A)  30 A 
B)  2.1 mA 
C)  22 mA 
D)  46 mA

Question 8

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

Accepted Answer

A)  Both wires have the same resistance. 
B)  The longer wire has 1/3 the resistance of the shorter wire. 
C)  The longer wire has 3 times the resistance of the shorter wire. 
D)  The longer wire has 9 times times the resistance of the shorter wire. 
E)  The longer wire has 27 times times the resistance of the shorter wire.

Question 9

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

Accepted Answer

A)  power 
B)  resistivity 
C)  1/(resistivity) 
D)  resistance 
E)  1/(resistance)

Question 10

A 150-W light bulb is designed to operate at 110 V dc. How much current does it draw?

Accepted Answer

A)  0.73 A 
B)  1.4 A 
C)  2.0 A 
D)  15 A

Question 11

A 25-m wire of diameter 0.30 mm draws 0.499 A when connected across a 3.0-V potential difference.
(a) What is the resistance of the wire?
(b) What is the resistivity of the material from which the wire is made?

Accepted Answer

The answer of A 25-m wire of diameter 0.30 mm...

Question 12

A 25-W soldering iron runs on 110 V dc. What is its resistance?

Accepted Answer

A)  0.0020 Ω 
B)  4.4 Ω 
C)  0.48 kΩ 
D)  2.8 kΩ

Question 13

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?

Accepted Answer

A)  Both wires have the same resistivity. 
B)  The longer wire has 3 times the resistivity of the shorter wire. 
C)  The longer wire has 9 times times the resistivity of the shorter wire. 
D)  The longer wire has 27 times times the resistivity of the shorter wire.

Question 14

A certain metal wire has a cross-sectional area of 1.0 cm2 and a resistivity of 1.7 × 10-8 Ω ∙ m. How long would it have to be to have a resistance of 1.0 Ω?

Accepted Answer

A)  5.9 × 106 m 
B)  5.9 m 
C)  5.9 × 104 m 
D)  590 m 
E)  5.9 km

Question 15

When current is flowing in an ordinary metal wire, the magnitude of the average velocity of the electrons is closest to

Accepted Answer

A)  10 m/s. 
B)  the speed of light. 
C)  1 mm/s. 
D)  1 km/s. 
E)  1 m/s.

Question 16

A total of 2.0 × 1013 electrons pass a given point in a wire in 15 s. What is the current in the wire? (e = 1.60 × 10-19 C)

Accepted Answer

A)  1.3 mA 
B)  1.3 A 
C)  0.21 μA 
D)  3.2 μA

Question 17

A 1.0-mm diameter extension cord is made of metal having a resistivity of 1.68 × 10-8 Ω ∙ m. When it carries a current of 15 A, what is the potential difference between two points in the cord that are 100 m apart?

Accepted Answer

A)  12 V 
B)  23 V 
C)  32 V 
D)  41 V

Question 18

What is the resistance of 1.0 m of a solid cylindrical metal cable having a diameter of 0.40 inches and a resistivity of 1.68 × 10-8 Ω ∙ m?

Accepted Answer

A)  0.00012 Ω 
B)  0.00021 Ω 
C)  0.0012 Ω 
D)  0.0021 Ω

Question 19

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

Accepted Answer

A)  It is increased by a factor of 2. 
B)  It is increased by a factor of 4. 
C)  It is reduced by a factor of 2. 
D)  It is reduced by a factor of 4. 
E)  It does not change.

Question 20

A tube of mercury with resistivity 9.84 × 10-7 Ω ∙ m has a uniform electric field of 23 N/C inside the mercury. How much current is flowing in the tube, if the radius of the tube is 0.495 mm?

Accepted Answer

A)  18 A 
B)  180 A 
C)  29 A 
D)  280 A

Exam 22: Current and Resistance

The resistivity of the material of a wire is 1.76 × 10^-8 Ω ∙ m. If the diameter of the wire is 2.00 mm and its length is 2.00 m, what is its resistance?

How much does it cost to operate a 25-W soldering iron for 8.0 hours if energy costs 8.0¢/kWh?

For the graph shown in the figure, what physical quantity does the slope of the graph represent for a dc circuit?

A battery supplies 6.0 mA to a 12-Ω resistor for 1.5 h. How much electric energy does this resistor dissipate in this time?

A flashlight draws 0.133 A from a 3.0-V battery pack. In 2.0 minutes (a) how much charge flows from the battery, (b) how much energy does the battery supply, and (c) how many electrons have passed any point in the circuit every second?

During a period of high power demand, the voltage output of the power company is reduced by 5.0%. By what percentage is the power in a resistor decreased?

A 120-Ω laboratory resistor is rated at 0.25 W. How much current can safely flow through the resistor?

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

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

A 150-W light bulb is designed to operate at 110 V dc. How much current does it draw?

A 25-m wire of diameter 0.30 mm draws 0.499 A when connected across a 3.0-V potential difference. (a) What is the resistance of the wire? (b) What is the resistivity of the material from which the wire is made?

A 25-W soldering iron runs on 110 V dc. What is its resistance?

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?

A certain metal wire has a cross-sectional area of 1.0 cm² and a resistivity of 1.7 × 10^-8 Ω ∙ m. How long would it have to be to have a resistance of 1.0 Ω?

When current is flowing in an ordinary metal wire, the magnitude of the average velocity of the electrons is closest to

A total of 2.0 × 10¹³ electrons pass a given point in a wire in 15 s. What is the current in the wire? (e = 1.60 × 10^-19C)

A 1.0-mm diameter extension cord is made of metal having a resistivity of 1.68 × 10^-8 Ω ∙ m. When it carries a current of 15 A, what is the potential difference between two points in the cord that are 100 m apart?

What is the resistance of 1.0 m of a solid cylindrical metal cable having a diameter of 0.40 inches and a resistivity of 1.68 × 10^-8 Ω ∙ m?

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

A tube of mercury with resistivity 9.84 × 10^-7 Ω ∙ m has a uniform electric field of 23 N/C inside the mercury. How much current is flowing in the tube, if the radius of the tube is 0.495 mm?