Question 1

If the length and diameter of a wire of circular cross section are both tripled, the resistance will be

Accepted Answer

A) unchanged. 
B) tripled. 
C) increased by a factor of 9. 
D) 1/3 of what it originally was. 
E) 1/9 of what it originally was. 
A) unchanged. 
B) tripled. 
C) increased by a factor of 9. 
D) 1/3 of what it originally was. 
E) 1/9 of what it originally was.

Question 2

A 6.0-V battery that can store $500.0 \mathrm {~J}$ of energy is connected to a resistor. How much charge must flow between the battery's terminals to completely drain the battery if it is fully charged? Assume that the voltage of the battery remains the same until it is totally drained.

Accepted Answer

A) 83 C 
B) 0.010 C 
C) 3000 C 
D) 0.07 C 
A) 83 C 
B) 0.010 C 
C) 3000 C 
D) 0.07 C

Question 3

How much charge must pass by a point in a wire in 10 s for the current inb the wire to be 0.50 A?

Accepted Answer

A) 20 C 
B) 2.0 C 
C) 5.0 C 
D) 0.050 C 
A) 20 C 
B) 2.0 C 
C) 5.0 C 
D) 0.050 C

Question 4

A current of 5.0 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)

Accepted Answer

A) 0.20 
B) 20 
C) 2.0 
D) 3.1 x $10 ^ { 20 }$ 
E) 31 x $10 ^ { 20 }$ 
A) 0.20 
B) 20 
C) 2.0 
D) 3.1 x $10 ^ { 20 }$ 
E) 31 x $10 ^ { 20 }$

Question 5

Which one of the following quantities is equivalent to 1 W?

Accepted Answer

A) 1 V/A 
B) 1 Ω ∙ m 
C) 1 V ∙ A 
D) 1 V/Ω 
E) 1 A ∙ s 
A) 1 V/A 
B) 1 Ω ∙ m 
C) 1 V ∙ A 
D) 1 V/Ω 
E) 1 A ∙ s

Question 6

A 100-W driveway light bulb is on 10 hours per day. If the power company charges 10¢ for each kilowatt-hour of electricity used, estimate the yearly cost to operate the bulb if it is used every day for a 365-day year.

Accepted Answer

A) $3.65 
B) $7.30 
C) $37 
D) $73 
A) $3.65 
B) $7.30 
C) $37 
D) $73

Question 7

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¢ 
A) $1.50 
B) 25¢ 
C) 16¢ 
D) 1.6¢

Question 8

When a current flows through a metal wire, the moving charges are

Accepted Answer

A) only protons. 
B) only electrons. 
C) both protons and electrons. 
D) positive metal ions. 
E) negative metal ions. 
A) only protons. 
B) only electrons. 
C) both protons and electrons. 
D) positive metal ions. 
E) negative metal ions.

Question 9

A electric heater that draws 13.5 A of dc current has been left on for 10 min. How many electrons that have passed through the heater during that time? (e = 1.60 × 10-19 C)

Accepted Answer

A) 1.5 × 1022 
B) 5.1 × 1022 
C) 1.8 × 103 
D) 8.1 × 103 
E) 1.0 × 1023 
A) 1.5 × 1022 
B) 5.1 × 1022 
C) 1.8 × 103 
D) 8.1 × 103 
E) 1.0 × 1023

Question 10

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

Question 11

When a 1.0-m length of metal wire is connected to a $1.5 - \mathrm { V }$ battery, a current of $8.0 \mathrm {~mA}$ flows through it. What is the diameter of the wire? The resistivity of the metal is 2.24 × 10-8 ? ? m.

Accepted Answer

A) 12 ?m 
B) 6.0 ?m 
C) 24 ?m 
D) 2.2 ?m 
A) 12 ?m 
B) 6.0 ?m 
C) 24 ?m 
D) 2.2 ?m

Question 12

If 3.0 × 1015 electrons flow through a section of a wire of diameter 2.0 mm in 4.0 s, what is the current in the wire? (e = 1.60 × 10-19 C)

Accepted Answer

A) 0.12 mA 
B) 0.24 mA 
C) 7.5 × 107 A 
D) 7.5 × 1014 A 
A) 0.12 mA 
B) 0.24 mA 
C) 7.5 × 107 A 
D) 7.5 × 1014 A

Question 13

What is the resistance of a cylindrical metal rod 1.0 cm in diameter and 45 m long, if the resistivity of the metal is 1.4 × 10-8 Ω ∙ m?

Accepted Answer

A) 0.0063 Ω 
B) 0.0080 Ω 
C) 0.80 Ω 
D) 6.3 Ω 
A) 0.0063 Ω 
B) 0.0080 Ω 
C) 0.80 Ω 
D) 6.3 Ω

Question 14

An electronic component with a 17-? resistor is rated for use at power levels not exceeding $14 \mathrm {~W}$ How much current can safely flow through the component?

Accepted Answer

A) 0.91 A 
B) 1.21 A 
C) 238 A 
D) 0.22 A 
A) 0.91 A 
B) 1.21 A 
C) 238 A 
D) 0.22 A

Question 15

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

Question 16

How much energy does a 100-W light bulb use in 8.0 hours?

Accepted Answer

A) 0.0080 kWh 
B) 0.80 kWh 
C) 13 kWh 
D) 800 kWh 
A) 0.0080 kWh 
B) 0.80 kWh 
C) 13 kWh 
D) 800 kWh

Question 17

The voltage drop across a metal bar is $5.0 \mathrm {~V}$ while a current of $10.0 \mathrm {~mA}$ flows through it. How much power does this bar dissipate?

Accepted Answer

A) 50 mW 
B) 500 ?W 
C) 2.5 kW 
D) 0.50 kW 
A) 50 mW 
B) 500 ?W 
C) 2.5 kW 
D) 0.50 kW

Question 18

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

Question 19

A 200-Ω resistor is rated at 1/4 W. What is the maximum current it can safely draw?

Accepted Answer

A) 0.035 A 
B) 0.35 A 
C) 50 A 
D) 0.25 A 
A) 0.035 A 
B) 0.35 A 
C) 50 A 
D) 0.25 A

Question 20

The figure shows a graph of the resistance of a wire as a function of its length. What physical quantities does the slope of this graph represent?

Accepted Answer

A) the cross-sectional area of the wire 
B) the resistivity of the material of which the wire is made 
C) the product of the resistivity and the cross-sectional area of the wire 
D) the resistivity of the material divided by the cross-sectional area of the wire 
E) the reciprocal of the resistivity of the material 
A) the cross-sectional area of the wire 
B) the resistivity of the material of which the wire is made 
C) the product of the resistivity and the cross-sectional area of the wire 
D) the resistivity of the material divided by the cross-sectional area of the wire 
E) the reciprocal of the resistivity of the material

Exam 22: Current and Resistance

If the length and diameter of a wire of circular cross section are both tripled, the resistance will be

How much charge must pass by a point in a wire in 10 s for the current inb the wire to be 0.50 A?

A current of 5.0 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)

Which one of the following quantities is equivalent to 1 W?

A 100-W driveway light bulb is on 10 hours per day. If the power company charges 10¢ for each kilowatt-hour of electricity used, estimate the yearly cost to operate the bulb if it is used every day for a 365-day year.

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

When a current flows through a metal wire, the moving charges are

A electric heater that draws 13.5 A of dc current has been left on for 10 min. How many electrons that have passed through the heater during that time? (e = 1.60 × 10-19 C)

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?

When a 1.0-m length of metal wire is connected to a 1.5−V1.5 - \mathrm { V }1.5−V battery, a current of 8.0 mA8.0 \mathrm {~mA}8.0 mA flows through it. What is the diameter of the wire? The resistivity of the metal is 2.24 × 10-8 ? ? m.

If 3.0 × 1015 electrons flow through a section of a wire of diameter 2.0 mm in 4.0 s, what is the current in the wire? (e = 1.60 × 10-19 C)

What is the resistance of a cylindrical metal rod 1.0 cm in diameter and 45 m long, if the resistivity of the metal is 1.4 × 10-8 Ω ∙ m?

An electronic component with a 17-? resistor is rated for use at power levels not exceeding 14 W14 \mathrm {~W}14 W How much current can safely flow through the component?

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

How much energy does a 100-W light bulb use in 8.0 hours?

The voltage drop across a metal bar is 5.0 V5.0 \mathrm {~V}5.0 V while a current of 10.0 mA10.0 \mathrm {~mA}10.0 mA flows through it. How much power does this bar dissipate?

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?

A 200-Ω resistor is rated at 1/4 W. What is the maximum current it can safely draw?

The figure shows a graph of the resistance of a wire as a function of its length. What physical quantities does the slope of this graph represent?

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A current of 5.0 A flows through an electrical device for 10 seconds. How many electrons flow through this device during this time? (e = 1.60 × 10^-19C)

A electric heater that draws 13.5 A of dc current has been left on for 10 min. How many electrons that have passed through the heater during that time? (e = 1.60 × 10^-19C)

When a 1.0-m length of metal wire is connected to a $1.5 - \mathrm { V }$ battery, a current of $8.0 \mathrm {~mA}$ flows through it. What is the diameter of the wire? The resistivity of the metal is 2.24 × 10^-8 ? ? m.

If 3.0 × 10¹⁵ electrons flow through a section of a wire of diameter 2.0 mm in 4.0 s, what is the current in the wire? (e = 1.60 × 10^-19C)

What is the resistance of a cylindrical metal rod 1.0 cm in diameter and 45 m long, if the resistivity of the metal is 1.4 × 10^-8 Ω ∙ m?

An electronic component with a 17-? resistor is rated for use at power levels not exceeding $14 \mathrm {~W}$ How much current can safely flow through the component?

The voltage drop across a metal bar is $5.0 \mathrm {~V}$ while a current of $10.0 \mathrm {~mA}$ flows through it. How much power does this bar dissipate?

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?