Question 1

Internal battery resistance: In the figure a current of 6.0 A is drawn from the battery. What is the terminal voltage Vab of the battery?

Accepted Answer

A)  0.00 V 
B)  +12 V 
C)  +24 V 
D)  -12 V 
E)  -24 V 
A)  0.00 V 
B)  +12 V 
C)  +24 V 
D)  -12 V 
E)  -24 V A

Question 2

Power: A 110-V hair dryer is rated at 1200 W. What current will it draw when operating from a 110-V electrical outlet?

Accepted Answer

A)  90 mA 
B)  1.0 A 
C)  5.0 A 
D)  11 A 
E)  14 A 
A)  90 mA 
B)  1.0 A 
C)  5.0 A 
D)  11 A 
E)  14 A D

Question 3

Resistivity: 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)False  False

Question 4

Power: The power rating of a 400-Ω resistor is 0.800 W.
(a) What is the maximum voltage that can be applied across this resistor without damaging it?
(b) What is the maximum current this resistor can draw without damaging it?

Accepted Answer

(a) 17.9 V

Question 5

Electric field in a wire: A tube of mercury with resistivity 9.84 × 10-7 Ω ∙ m has an electric field inside the column of mercury of magnitude 23 N/C that is directed along the length of the tube. How much current is flowing through this tube if its diameter is 1.0 mm?

Accepted Answer

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

Question 6

Power: The voltage and power ratings of a particular light bulb, which are its normal operating values, are 110 V and 60 W. Assume the resistance of the filament of the bulb is constant and is independent of operating conditions. If the light bulb is operated at a reduced voltage and the power drawn by the bulb is 36 W, what is the operating voltage of the bulb?

Accepted Answer

A)  66 V 
B)  72 V 
C)  78 V 
D)  85 V 
E)  90 V 
A)  66 V 
B)  72 V 
C)  78 V 
D)  85 V 
E)  90 V

Question 7

Current density: 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/   
B)  6.2 A/   
C)  12 A/   
D)  17 A/   
A)  25 A/   
B)  6.2 A/   
C)  12 A/   
D)  17 A/

Question 8

Ohm's law: How much current will be flowing through a 40.0 m length of cylindrical metal wire with radius 0.0 mm if it is connected to a source supplying 16.0 V? The resistivity of this metal is 1.68 × 10-8 Ω ∙ m.

Accepted Answer

A)  1200 A 
B)  9.5 × 108 A 
C)  68 nA 
D)  710 A 
A)  1200 A 
B)  9.5 × 108 A 
C)  68 nA 
D)  710 A

Question 9

Drift velocity: 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/s 
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/s

Question 10

Ohm's law: A cylindrical wire of radius 2.0 mm carries a current of 2.5 A. The potential difference between points on the wire that are 46 m apart is 3.7 V.
(a) What is the electric field in the wire?
(b) What is the resistivity of the material of which the wire is made?

Accepted Answer

a) 0.080 V

Question 11

Resistivity: What must be the diameter of a cylindrical 120-m long metal wire if its resistance is to be 6.0 Ω? The resistivity of this metal is 1.68 × 10-8 Ω ∙ m.

Accepted Answer

A)  0.065 mm 
B)  0.65 mm 
C)  0.65 cm 
D)  0.325 mm 
E)  0.0325 mm 
A)  0.065 mm 
B)  0.65 mm 
C)  0.65 cm 
D)  0.325 mm 
E)  0.0325 mm

Question 12

Drift velocity: The diameter of a copper wire is 2.05 mm. 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/s 
A)  0.044 mm/s 
B)  0.44 mm/s 
C)  0.44 cm/s 
D)  0.44 m/s 
E)  4.4 cm/s

Question 13

Power: The heater element of a particular 120-V toaster is a 8.9-m length of nichrome wire, whose diameter is 0.86 mm. The resistivity of nichrome at the operating temperature of the toaster is 1.3 × 10-6 Ω ∙ m. If the toaster is operated at a voltage of 120 V, how much power does it draw?

Accepted Answer

A)  720 W 
B)  700 W 
C)  750 W 
D)  770 W 
E)  800 W 
A)  720 W 
B)  700 W 
C)  750 W 
D)  770 W 
E)  800 W

Question 14

Power: A 1500-W heater is connected to a 120-V line. How much heat energy does it produce in 2.0 hours?

Accepted Answer

A)  1.5 kJ 
B)  3.0 kJ 
C)  0.18 MJ 
D)  11 MJ 
E)  18 MJ 
A)  1.5 kJ 
B)  3.0 kJ 
C)  0.18 MJ 
D)  11 MJ 
E)  18 MJ

Question 15

Current: 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 × 10-19C)

Accepted Answer

A)  1.2 ×   
B)  4.4 ×   
C)  5.3 ×   
D)  3.3 ×   
A)  1.2 ×   
B)  4.4 ×   
C)  5.3 ×   
D)  3.3 ×

Question 16

Internal battery resistance: In the figure, when the terminal voltage Vab of the battery is equal to 20 V, how much current passes through the battery, including its direction?

Accepted Answer

A)  4 A, from a to b 
B)  5 A, from a to b 
C)  6 A, from a to b 
D)  4 A, from b to a 
E)  5 A, from b to a 
A)  4 A, from a to b 
B)  5 A, from a to b 
C)  6 A, from a to b 
D)  4 A, from b to a 
E)  5 A, from b to a

Question 17

Ohm's law: 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 mA 
A)  17.5 A 
B)  30.9 A 
C)  61.8 A 
D)  388 mA 
E)  776 mA

Question 18

Ohm's law: When a potential difference of 10 V is placed across a certain solid cylindrical resistor, the current through it is 2 A. If the diameter of this resistor is now tripled, the current will be

Accepted Answer

A)  2/9 A. 
B)  2/3 A. 
C)  2 A. 
D)  3 A. 
E)  18 A. 
A)  2/9 A. 
B)  2/3 A. 
C)  2 A. 
D)  3 A. 
E)  18 A.

Question 19

Current: 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?

Accepted Answer

A)  190 nA 
B)  23 μA 
C)  30 nA 
D)  11 μA 
A)  190 nA 
B)  23 μA 
C)  30 nA 
D)  11 μA

Question 20

Resistivity: 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. 
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.

Exam 21: Electric Charge and Electric Field

Internal battery resistance: In the figure a current of 6.0 A is drawn from the battery. What is the terminal voltage Vab of the battery?

Power: A 110-V hair dryer is rated at 1200 W. What current will it draw when operating from a 110-V electrical outlet?

Resistivity: 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.

Power: The power rating of a 400-Ω resistor is 0.800 W. (a) What is the maximum voltage that can be applied across this resistor without damaging it? (b) What is the maximum current this resistor can draw without damaging it?

Electric field in a wire: A tube of mercury with resistivity 9.84 × 10-7 Ω ∙ m has an electric field inside the column of mercury of magnitude 23 N/C that is directed along the length of the tube. How much current is flowing through this tube if its diameter is 1.0 mm?

Ohm's law: How much current will be flowing through a 40.0 m length of cylindrical metal wire with radius 0.0 mm if it is connected to a source supplying 16.0 V? The resistivity of this metal is 1.68 × 10-8 Ω ∙ m.

Drift velocity: 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?

Ohm's law: A cylindrical wire of radius 2.0 mm carries a current of 2.5 A. The potential difference between points on the wire that are 46 m apart is 3.7 V. (a) What is the electric field in the wire? (b) What is the resistivity of the material of which the wire is made?

Resistivity: What must be the diameter of a cylindrical 120-m long metal wire if its resistance is to be 6.0 Ω? The resistivity of this metal is 1.68 × 10-8 Ω ∙ m.

Power: The heater element of a particular 120-V toaster is a 8.9-m length of nichrome wire, whose diameter is 0.86 mm. The resistivity of nichrome at the operating temperature of the toaster is 1.3 × 10-6 Ω ∙ m. If the toaster is operated at a voltage of 120 V, how much power does it draw?

Power: A 1500-W heater is connected to a 120-V line. How much heat energy does it produce in 2.0 hours?

Current: 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 × 10-19C)

Internal battery resistance: In the figure, when the terminal voltage Vab of the battery is equal to 20 V, how much current passes through the battery, including its direction?

Ohm's law: 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.

Ohm's law: When a potential difference of 10 V is placed across a certain solid cylindrical resistor, the current through it is 2 A. If the diameter of this resistor is now tripled, the current will be

Current: 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?

Resistivity: 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

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Internal battery resistance: In the figure a current of 6.0 A is drawn from the battery. What is the terminal voltage V_ab of the battery?

Electric field in a wire: A tube of mercury with resistivity 9.84 × 10^-7 Ω ∙ m has an electric field inside the column of mercury of magnitude 23 N/C that is directed along the length of the tube. How much current is flowing through this tube if its diameter is 1.0 mm?

Ohm's law: How much current will be flowing through a 40.0 m length of cylindrical metal wire with radius 0.0 mm if it is connected to a source supplying 16.0 V? The resistivity of this metal is 1.68 × 10^-8 Ω ∙ m.

Drift velocity: 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?

Resistivity: What must be the diameter of a cylindrical 120-m long metal wire if its resistance is to be 6.0 Ω? The resistivity of this metal is 1.68 × 10^-8 Ω ∙ m.

Power: The heater element of a particular 120-V toaster is a 8.9-m length of nichrome wire, whose diameter is 0.86 mm. The resistivity of nichrome at the operating temperature of the toaster is 1.3 × 10^-6 Ω ∙ m. If the toaster is operated at a voltage of 120 V, how much power does it draw?

Current: 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^-19C)

Internal battery resistance: In the figure, when the terminal voltage V_ab of the battery is equal to 20 V, how much current passes through the battery, including its direction?

Ohm's law: 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.

Current: 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?