Question 1

When a voltage difference is applied to a piece of metal wire, a -8 Ω ∙ m, and the resistivity of silver is 1.59 × 10-8 Ω ∙ m.)  A)  21 mA B)  19 mA C)  11 mA D)  5.3 mA" class="answers-bank-image d-inline" rel="preload" > current flows through it. If this metal wire is now replaced with a silver wire having twice the diameter of the original wire, how much current will flow through the silver wire? The lengths of both wires are the same, and the voltage difference remains unchanged. (The resistivity of the original metal is 1.68 × 10-8 Ω ∙ m, and the resistivity of silver is 1.59 × 10-8 Ω ∙ m.)

Accepted Answer

A)   21 mA
B)   19 mA
C)   11 mA
D)   5.3 mAE) A) and C)
F) B) and C)

Question 2

The resistivity of gold is  at room temperature. A gold wire that is 0.9 mm in diameter and 14 cm long carries a current of 940 mA. What is the electric field in the wire?

Accepted Answer

A)   0.036 V/m
B)   0.0090 V/m
C)   0.028 V/m
D)   0.046 V/m
E)   0.090 V/mF) B) and E)
G) C) and D)

Question 3

The current supplied by a battery as a function of time is -19 C)  A)  1.2 ×   B)  4.4 ×   C)  5.3 ×   D)  3.3 ×  " class="answers-bank-image d-inline" rel="preload" > What is the total number of electrons transported from the positive electrode to the negative electrode from the time the battery is first used until it is essentially dead? (e = 1.60 × 10-19 C)

Accepted Answer

A)   1.2 × -19 
C)   
A)   1.2 ×   
B)   4.4 ×   
C)   5.3 ×   
D)   3.3 ×  " class="answers-bank-image d-inline" rel="preload" >
B)   4.4 × -19 
C)   
A)   1.2 ×   
B)   4.4 ×   
C)   5.3 ×   
D)   3.3 ×  " class="answers-bank-image d-inline" rel="preload" >
C)   5.3 × -19 
C)   
A)   1.2 ×   
B)   4.4 ×   
C)   5.3 ×   
D)   3.3 ×  " class="answers-bank-image d-inline" rel="preload" >
D)   3.3 × -19 
C)   
A)   1.2 ×   
B)   4.4 ×   
C)   5.3 ×   
D)   3.3 ×  " class="answers-bank-image d-inline" rel="preload" >E) A) and C)
F) B) and C) A

Question 4

A wire has a cross-sectional area of 0.10 mm2. If there are 4.0 × 1028 atoms per cubic meter in this wire, and if each atom contributes 2 free electrons, what is the drift velocity of the electrons when the current in the wire is 6.0 A? (e = 1.60 × 10-19 C)

Accepted Answer

A)   0.0047 m/s
B)   0.0092 m/s
C)   0.94 m/s
D)   0.019 m/sE) A) and D)
F) A) and C)

Question 5

A certain fuse "blows" if the current in it exceeds 1.0 A, at which instant the fuse melts with a current density of  What is the diameter of the wire in the fuse?

Accepted Answer

A)   0.45 mm
B)   0.63 mm
C)   0.68 mm
D)   0.91 mmE) B) and D)
F) A) and D) A

Question 6

What length of a certain metal wire of diameter 0.15 mm is needed for the wire to have a resistance of 15 Ω? The resistivity of this metal is 1.68 × 10-8 Ω ∙ m.

Accepted Answer

A)   16 mm
B)   16 cm
C)   1.6 m
D)   16 m
E)   160 mF) A) and B)
G) D) and E)

Question 7

Calculate the current through a 10.0-m long 22 gauge (having radius 0.321 mm)  nichrome wire if it is connected to a 12.0-V battery. The resistivity of nichrome is 100 × 10-8 Ω ∙ m.

Accepted Answer

A)   17.5 A
B)   30.9 A
C)   61.8 A
D)   388 mA
E)   776 mAF) B) and C)
G) A) and E)

Question 8

The figure shows a steady electric current passing through a wire with a narrow region. What happens to the drift velocity of the moving charges as they go from region A to region B and then to region C?

Accepted Answer

A)   The drift velocity decreases from A to B and increases from B to C.
B)   The drift velocity increases all the time.
C)   The drift velocity remains constant.
D)   The drift velocity decreases all the time.
E)   The drift velocity increases from A to B and decreases from B to C.F) B) and C)
G) B) and E)

Question 9

As current flows through a uniform wire, the wire gets hotter because the electrons stop moving and therefore transform their lost kinetic energy into thermal energy in the wire.

Accepted Answer

A)   True
B)   FalseC) A) and B)
D) undefined B

Question 10

Two cables of the same length are made of the same material, except that one cable has twice the diameter of the other cable. When the same potential difference is maintained across both cables, which of the following statements are true? (There may be more than one correct choice.)

Accepted Answer

A)   The same current flows through both cables.
B)   Both cables carry the same current density.
C)   The electrons have the same drift velocity in both cables.
D)   The current in the thin cable is twice as great as the current in the thick cable.
E)   The current in the thin cable is four times as great as the current in the thick cable.F) A) and E)
G) C) and E)

Question 11

A 2.0 mm diameter wire of length 20 m has a resistance of 0.25 Ω. What is the resistivity of the wire?

Accepted Answer

A)   5.0 × 10-7 Ω ∙ m
B)   3.9 × 10-8 Ω ∙ m
C)   4.0 × 10-7 Ω ∙ m
D)   16 × 10-8 Ω ∙ m
E)   0.25 Ω ∙ mF) A) and E)
G) A) and C)

Question 12

The diameter of a 12-gauge copper wire is 0.081 in. The maximum safe current it can carry (in order to prevent fire danger in building construction)  is 20 A. At this current, what is the drift velocity of the electrons? The number of electron carriers in 1.0 cm3 of copper is 8.5 × 1022 and e = 1.60 × 10-19 C.

Accepted Answer

A)   0.044 mm/s
B)   0.44 mm/s
C)   0.44 cm/s
D)   0.44 m/s
E)   4.4 cm/sF) A) and D)
G) A) and E)

Question 13

Nichrome wire, often used for heating elements, has resistivity of 1.0 × 10-6 Ω ∙ m at room temperature. What length of No. 30 wire (of diameter 0.250 mm)  is needed to wind a resistor that has 50 ohms at room temperature?

Accepted Answer

A)   3.66 m
B)   2.45 m
C)   0.61 m
D)   6.54 m
E)   22.4 mF) A) and B)
G) C) and E)

Question 14

A wire of resistivity ρ must be replaced in a circuit by a wire of the same material but 4 times as long. If, however, the resistance of the new wire is to be the same as the resistance of the original wire, the diameter of the new wire must be

Accepted Answer

A)   the same as the diameter of the original wire.
B)   1/2 the diameter of the original wire.
C)   1/4 the diameter of the original wire.
D)   2 times the diameter of the original wire.
E)   4 times the diameter of the original wire.F) B) and C)
G) A) and E)

Question 15

If a current of 2.4 A is flowing in a cylindrical wire of diameter 2.0 mm, what is the average current density in this wire?

Accepted Answer

A)   7.6 × 105 A/m2
B)   5.2 × 10-6 A/m2
C)   1.9 × 105 A/m2
D)   3.6 × 105 A/m2
E)   21 × 10-6 A/m2F) B) and C)
G) B) and D)

Question 16

The figure shows a 2.0-cm diameter roller that turns at 90 rpm. A 4.0-cm wide plastic film is being wrapped onto the roller, and this plastic carries an excess electric charge having a uniform surface charge density of 5.0 nC/cm2. What is the current of the moving film? 2. What is the current of the moving film?   A)  190 nA B)  23 μA C)  30 nA D)  11 μA" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   190 nA
B)   23 μA
C)   30 nA
D)   11 μAE) B) and C)
F) A) and D)

Question 17

A proton beam that carries a total current of 1.3 mA has 10.0 mm diameter. The current density in the proton beam increases linearly with distance from the center. This is expressed mathematically as J(r)  = J0 (r/R) , where R is the radius of the beam and J0 is the current density at the edge. Determine the value of J0.

Accepted Answer

A)   25 A/ 0 (r/R) , where R is the radius of the beam and J0 is the current density at the edge. Determine the value of J0. 
A)   25 A/   
B)   6.2 A/   
C)   12 A/   
D)   17 A/  " class="answers-bank-image d-inline" rel="preload" >
B)   6.2 A/ 0 (r/R) , where R is the radius of the beam and J0 is the current density at the edge. Determine the value of J0. 
A)   25 A/   
B)   6.2 A/   
C)   12 A/   
D)   17 A/  " class="answers-bank-image d-inline" rel="preload" >
C)   12 A/ 0 (r/R) , where R is the radius of the beam and J0 is the current density at the edge. Determine the value of J0. 
A)   25 A/   
B)   6.2 A/   
C)   12 A/   
D)   17 A/  " class="answers-bank-image d-inline" rel="preload" >
D)   17 A/ 0 (r/R) , where R is the radius of the beam and J0 is the current density at the edge. Determine the value of J0. 
A)   25 A/   
B)   6.2 A/   
C)   12 A/   
D)   17 A/  " class="answers-bank-image d-inline" rel="preload" >E) A) and B)
F) A) and C)

Question 18

When electric current is flowing in a metal, the electrons are moving

Accepted Answer

A)   at nearly the speed of light.
B)   at the speed of light.
C)   at the speed of sound in the metal.
D)   at the speed of sound in air.
E)   at none of the above speeds.F) A) and B)
G) B) and E)

Question 19

If the current density in a wire or radius R is given by J = kr, 0 < r < R, what is the current in the wire?

Accepted Answer

A)   2πkR3/3
B)   3πkR3/2
C)   kR3/3
D)   kR2
E)   kR2/2F) B) and D)
G) None of the above

Question 20

A silver wire has a cross sectional area A = 2.0 mm2. A total of 9.4 × 1018 electrons pass through the wire in 3.0 s. The conduction electron density in silver is 5.8 × 1028 electrons/m3 and e = 1.60 × 10-19 C. What is the drift velocity of these electrons?

Accepted Answer

A)   2.7 × 10-5 m/s
B)   9.1 × 10-5 m/s
C)   5.2 × 10-5 m/s
D)   1.1 × 10-5 m/s
E)   7.4 × 10-5 m/sF) None of the above
G) C) and E)

Exam 27: Current and Resistance

Correct Answer
verified

The resistivity of gold is at room temperature. A gold wire that is 0.9 mm in diameter and 14 cm long carries a current of 940 mA. What is the electric field in the wire?

Correct Answer
verified

The current supplied by a battery as a function of time is What is the total number of electrons transported from the positive electrode to the negative electrode from the time the battery is first used until it is essentially dead? (e = 1.60 × 10^-19 C)

Correct Answer
verified
A

A wire has a cross-sectional area of 0.10 mm². If there are 4.0 × 10²⁸ atoms per cubic meter in this wire, and if each atom contributes 2 free electrons, what is the drift velocity of the electrons when the current in the wire is 6.0 A? (e = 1.60 × 10^-19 C)

Correct Answer
verified

A certain fuse "blows" if the current in it exceeds 1.0 A, at which instant the fuse melts with a current density of What is the diameter of the wire in the fuse?

Correct Answer
verified
A

What length of a certain metal wire of diameter 0.15 mm is needed for the wire to have a resistance of 15 Ω? The resistivity of this metal is 1.68 × 10^-8 Ω ∙ m.

Correct Answer
verified

Calculate the current through a 10.0-m long 22 gauge (having radius 0.321 mm) nichrome wire if it is connected to a 12.0-V battery. The resistivity of nichrome is 100 × 10^-8 Ω ∙ m.

Correct Answer
verified

The figure shows a steady electric current passing through a wire with a narrow region. What happens to the drift velocity of the moving charges as they go from region A to region B and then to region C?

Correct Answer
verified

As current flows through a uniform wire, the wire gets hotter because the electrons stop moving and therefore transform their lost kinetic energy into thermal energy in the wire.

Correct Answer
verified
B

Two cables of the same length are made of the same material, except that one cable has twice the diameter of the other cable. When the same potential difference is maintained across both cables, which of the following statements are true? (There may be more than one correct choice.)

Correct Answer
verified

A 2.0 mm diameter wire of length 20 m has a resistance of 0.25 Ω. What is the resistivity of the wire?

Correct Answer
verified

Correct Answer
verified

Nichrome wire, often used for heating elements, has resistivity of 1.0 × 10^-6 Ω ∙ m at room temperature. What length of No. 30 wire (of diameter 0.250 mm) is needed to wind a resistor that has 50 ohms at room temperature?

Correct Answer
verified

A wire of resistivity ρ must be replaced in a circuit by a wire of the same material but 4 times as long. If, however, the resistance of the new wire is to be the same as the resistance of the original wire, the diameter of the new wire must be

Correct Answer
verified

If a current of 2.4 A is flowing in a cylindrical wire of diameter 2.0 mm, what is the average current density in this wire?

Correct Answer
verified

The figure shows a 2.0-cm diameter roller that turns at 90 rpm. A 4.0-cm wide plastic film is being wrapped onto the roller, and this plastic carries an excess electric charge having a uniform surface charge density of 5.0 nC/cm². What is the current of the moving film?

Correct Answer
verified

Correct Answer
verified

When electric current is flowing in a metal, the electrons are moving

Correct Answer
verified

If the current density in a wire or radius R is given by J = kr, 0 < r < R, what is the current in the wire?

Correct Answer
verified

A silver wire has a cross sectional area A = 2.0 mm². A total of 9.4 × 10¹⁸ electrons pass through the wire in 3.0 s. The conduction electron density in silver is 5.8 × 10²⁸ electrons/m³ and e = 1.60 × 10^-19 C. What is the drift velocity of these electrons?

Correct Answer
verified

Exam 27: Current and Resistance

Correct AnswerverifiedShow Answer

The resistivity of gold is at room temperature. A gold wire that is 0.9 mm in diameter and 14 cm long carries a current of 940 mA. What is the electric field in the wire?

Correct AnswerverifiedShow Answer

The current supplied by a battery as a function of time is What is the total number of electrons transported from the positive electrode to the negative electrode from the time the battery is first used until it is essentially dead? (e = 1.60 × 10-19 C)

Correct AnswerverifiedA

A wire has a cross-sectional area of 0.10 mm2. If there are 4.0 × 1028 atoms per cubic meter in this wire, and if each atom contributes 2 free electrons, what is the drift velocity of the electrons when the current in the wire is 6.0 A? (e = 1.60 × 10-19 C)

Correct AnswerverifiedShow Answer

A certain fuse "blows" if the current in it exceeds 1.0 A, at which instant the fuse melts with a current density of What is the diameter of the wire in the fuse?

Correct AnswerverifiedA

What length of a certain metal wire of diameter 0.15 mm is needed for the wire to have a resistance of 15 Ω? The resistivity of this metal is 1.68 × 10-8 Ω ∙ m.

Correct AnswerverifiedShow Answer

Calculate the current through a 10.0-m long 22 gauge (having radius 0.321 mm) nichrome wire if it is connected to a 12.0-V battery. The resistivity of nichrome is 100 × 10-8 Ω ∙ m.

Correct AnswerverifiedShow Answer

The figure shows a steady electric current passing through a wire with a narrow region. What happens to the drift velocity of the moving charges as they go from region A to region B and then to region C?

Correct AnswerverifiedShow Answer

As current flows through a uniform wire, the wire gets hotter because the electrons stop moving and therefore transform their lost kinetic energy into thermal energy in the wire.

Correct AnswerverifiedB

Two cables of the same length are made of the same material, except that one cable has twice the diameter of the other cable. When the same potential difference is maintained across both cables, which of the following statements are true? (There may be more than one correct choice.)

Correct AnswerverifiedShow Answer

A 2.0 mm diameter wire of length 20 m has a resistance of 0.25 Ω. What is the resistivity of the wire?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Nichrome wire, often used for heating elements, has resistivity of 1.0 × 10-6 Ω ∙ m at room temperature. What length of No. 30 wire (of diameter 0.250 mm) is needed to wind a resistor that has 50 ohms at room temperature?

Correct AnswerverifiedShow Answer

A wire of resistivity ρ must be replaced in a circuit by a wire of the same material but 4 times as long. If, however, the resistance of the new wire is to be the same as the resistance of the original wire, the diameter of the new wire must be

Correct AnswerverifiedShow Answer

If a current of 2.4 A is flowing in a cylindrical wire of diameter 2.0 mm, what is the average current density in this wire?

Correct AnswerverifiedShow Answer

The figure shows a 2.0-cm diameter roller that turns at 90 rpm. A 4.0-cm wide plastic film is being wrapped onto the roller, and this plastic carries an excess electric charge having a uniform surface charge density of 5.0 nC/cm2. What is the current of the moving film?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

When electric current is flowing in a metal, the electrons are moving

Correct AnswerverifiedShow Answer

If the current density in a wire or radius R is given by J = kr, 0 < r < R, what is the current in the wire?

Correct AnswerverifiedShow Answer

A silver wire has a cross sectional area A = 2.0 mm2. A total of 9.4 × 1018 electrons pass through the wire in 3.0 s. The conduction electron density in silver is 5.8 × 1028 electrons/m3 and e = 1.60 × 10-19 C. What is the drift velocity of these electrons?

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified

The current supplied by a battery as a function of time is What is the total number of electrons transported from the positive electrode to the negative electrode from the time the battery is first used until it is essentially dead? (e = 1.60 × 10^-19 C)

Correct Answer
verified
A

A wire has a cross-sectional area of 0.10 mm². If there are 4.0 × 10²⁸ atoms per cubic meter in this wire, and if each atom contributes 2 free electrons, what is the drift velocity of the electrons when the current in the wire is 6.0 A? (e = 1.60 × 10^-19 C)

Correct Answer
verified

Correct Answer
verified
A

What length of a certain metal wire of diameter 0.15 mm is needed for the wire to have a resistance of 15 Ω? The resistivity of this metal is 1.68 × 10^-8 Ω ∙ m.

Correct Answer
verified

Calculate the current through a 10.0-m long 22 gauge (having radius 0.321 mm) nichrome wire if it is connected to a 12.0-V battery. The resistivity of nichrome is 100 × 10^-8 Ω ∙ m.

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
B

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Nichrome wire, often used for heating elements, has resistivity of 1.0 × 10^-6 Ω ∙ m at room temperature. What length of No. 30 wire (of diameter 0.250 mm) is needed to wind a resistor that has 50 ohms at room temperature?

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

The figure shows a 2.0-cm diameter roller that turns at 90 rpm. A 4.0-cm wide plastic film is being wrapped onto the roller, and this plastic carries an excess electric charge having a uniform surface charge density of 5.0 nC/cm². What is the current of the moving film?

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

A silver wire has a cross sectional area A = 2.0 mm². A total of 9.4 × 10¹⁸ electrons pass through the wire in 3.0 s. The conduction electron density in silver is 5.8 × 10²⁸ electrons/m³ and e = 1.60 × 10^-19 C. What is the drift velocity of these electrons?

Correct Answer
verified