Question 1

The temperature coefficient of resistivity for a "perfect" ohmic material would be:

Accepted Answer

A) positive and constant. 
B) zero. 
C) negative. 
D) positive and uniformly increasing. 
A) positive and constant. 
B) zero. 
C) negative. 
D) positive and uniformly increasing.

Question 2

A metal wire has a resistance of 14.00 Ω at a temperature of 25.0°C.If the same wire has a resistance of 14.55 Ω at 90.0°C,what is the resistance when its temperature is −32.0°C?

Accepted Answer

A) 2.21 Ω 
B) 13.5 Ω 
C) 5.13 Ω 
D) 39.2 Ω 
E) 13.0 Ω 
A) 2.21 Ω 
B) 13.5 Ω 
C) 5.13 Ω 
D) 39.2 Ω 
E) 13.0 Ω

Question 3

A copper cable needs to carry a current of 160 A with a power loss of only 2.0 W/m.What is the required radius of the copper cable? (The resistivity of copper is 1.7 × 10−8 Ω⋅m).

Accepted Answer

A) 0.43 cm 
B) 0.83 cm 
C) 1.7 cm 
D) 2.6 cm 
E) 0.33 cm 
A) 0.43 cm 
B) 0.83 cm 
C) 1.7 cm 
D) 2.6 cm 
E) 0.33 cm

Question 4

A 50-W light bulb is in a socket supplied with 140 V.What is the current in the bulb?

Accepted Answer

A) 0.36 A 
B) 2.8 A 
C) 90 A 
D) 7 000 A 
E) 3.8 A 
A) 0.36 A 
B) 2.8 A 
C) 90 A 
D) 7 000 A 
E) 3.8 A

Question 5

When the voltage across a nonohmic resistor is doubled,the current through it triples.What happens to the power delivered to this resistor?

Accepted Answer

A) This cannot be answered with the information given. 
B) The power decreases to 2/3 of the original amount. 
C) The power increases to 1.5 times the original amount. 
D) The power increases to 6 times the original amount. 
A) This cannot be answered with the information given. 
B) The power decreases to 2/3 of the original amount. 
C) The power increases to 1.5 times the original amount. 
D) The power increases to 6 times the original amount.

Question 6

If a light bulb has half the resistance of a 110-W light bulb,what would be its wattage? Assume both bulbs are attached to the same 160-V circuit.

Accepted Answer

A) 220 W 
B) 55 W 
C) 1.5 W 
D) 330 W 
E) More information is needed. 
A) 220 W 
B) 55 W 
C) 1.5 W 
D) 330 W 
E) More information is needed.

Question 7

If a lamp has resistance of 140 Ω when it operates at 130 W,what is the applied voltage?

Accepted Answer

A) 135 V 
B) 151 V 
C) 121 V 
D) 72.9 V 
E) 108 V 
A) 135 V 
B) 151 V 
C) 121 V 
D) 72.9 V 
E) 108 V

Question 8

​A light bulb is connected to a 12-V battery.Because light bulbs are non-Ohmic,the resistance of the bulb is not constant,but increases as the bulb gets hotter.As the bulb heats up,which value remains unchanged?

Accepted Answer

A) ​The power consumed by the bulb. 
B) ​The current through the bulb. 
C) ​The voltage across the bulb. 
D) ​All the above change. 
A) ​The power consumed by the bulb. 
B) ​The current through the bulb. 
C) ​The voltage across the bulb. 
D) ​All the above change.

Question 9

Wire A and Wire B are each carrying the same current.If the diameter of Wire A is twice that of Wire B,how does the drift velocity vdA in Wire A compare to that in in Wire B?

Accepted Answer

A) vdA = vdB 
B) vdA = 2 vdB 
C) vdA = vdB /2 
D) vdA = vdB /4 
A) vdA = vdB 
B) vdA = 2 vdB 
C) vdA = vdB /2 
D) vdA = vdB /4

Question 10

The resistivity of a material is doubled when heated a certain amount.What happens to the resistance of a resistor made of this material when heated the same amount?

Accepted Answer

A) It doubles. 
B) It quadruples. 
C) It halves. 
D) It stays the same. 
A) It doubles. 
B) It quadruples. 
C) It halves. 
D) It stays the same.

Question 11

A resistor is connected to a battery with negligible internal resistance.If you replace the resistor with one that has triple the resistance,by what factor does the power dissipated in the circuit change?

Accepted Answer

A) 1/3 
B) 1/9 
C) 3 
D) 9 
E)    
A) 1/3 
B) 1/9 
C) 3 
D) 9 
E)

Question 12

A Nichrome wire has a radius of 1.3 mm and a resistivity of 1.5 × 10−6 Ω⋅m.What is the resistance per unit length of this wire?

Accepted Answer

A) 0.37 Ω/m 
B) 8.0 Ω/m 
C) 3.6 Ω/m 
D) 0.28 Ω/m 
E) 1.2 Ω/m 
A) 0.37 Ω/m 
B) 8.0 Ω/m 
C) 3.6 Ω/m 
D) 0.28 Ω/m 
E) 1.2 Ω/m

Question 13

You measure a 20-V potential difference across a 7.0-Ω resistor.What is the current flowing through it?

Accepted Answer

A) 140 A 
B) 2.9 A 
C) 27 A 
D) 13 A 
E) 5.2 A 
A) 140 A 
B) 2.9 A 
C) 27 A 
D) 13 A 
E) 5.2 A

Question 14

A tungsten wire is used to determine the melting point of indium.The resistance of the tungsten wire is 3.000 Ω at 20.0°C and increases to 4.850 Ω as the indium starts to melt.αtungsten = 4.50 × 10−3 (°C)−1.What is the melting temperature of indium?

Accepted Answer

A) 132°C 
B) 157°C 
C) 351°C 
D) 731°C 
A) 132°C 
B) 157°C 
C) 351°C 
D) 731°C

Question 15

How long is a wire made from 100 cm3 of copper if its resistance is 4.0 ohms? The resistivity of copper is 1.7 × 10-5 Ω·m.

Accepted Answer

A) 4.9 m 
B) 1.7 × 102 m 
C) 2.6 × 102 m 
D) 1.5 × 103 m 
E) 24 m 
A) 4.9 m 
B) 1.7 × 102 m 
C) 2.6 × 102 m 
D) 1.5 × 103 m 
E) 24 m

Question 16

The unit of electric current,the ampere,is equivalent to which of the following?

Accepted Answer

A) V⋅Ω 
B) V/Ω 
C) Ω⋅m 
D) V/s 
A) V⋅Ω 
B) V/Ω 
C) Ω⋅m 
D) V/s

Question 17

If a metallic wire of cross-sectional area 4.0 × 10−6 m2 carries a current of 7.0 A and has a mobile charge density of 4.24 × 1028 carriers/m3,what is the average drift velocity of the mobile charge carriers? (charge value = 1.6 × 10−19 C)

Accepted Answer

A) 1.8E+3 m/s 
B) 1.7E+3 m/s 
C) 4.1E-4 m/s 
D) 2.6E-4 m/s 
E) 7.0E-6 m/s 
A) 1.8E+3 m/s 
B) 1.7E+3 m/s 
C) 4.1E-4 m/s 
D) 2.6E-4 m/s 
E) 7.0E-6 m/s

Question 18

A 16-Ω platinum wire at 20°C with a temperature coefficient of resistivity of 3.9 × 10−3 (°C)−1 will have what resistance at 80°C?

Accepted Answer

A) 12 Ω 
B) 13 Ω 
C) 20 Ω 
D) 16 Ω 
E) 3.7 Ω 
A) 12 Ω 
B) 13 Ω 
C) 20 Ω 
D) 16 Ω 
E) 3.7 Ω

Question 19

An electric car is designed to run off a bank of 14.0-V batteries with total energy storage of 3.00 × 107 J.If the electric motor draws 7 000 W,what current will be delivered to the motor?

Accepted Answer

A) 500 A 
B) 250 A 
C) 750 A 
D) 375 A 
E) 125 A 
A) 500 A 
B) 250 A 
C) 750 A 
D) 375 A 
E) 125 A

Question 20

A high-voltage transmission line carries 1 000 A at 700 kV for a distance of 200 miles.If the resistance in the wire is 1 Ω/mile,what is the power loss due to resistive losses?

Accepted Answer

A) 20 kW 
B) 200 kW 
C) 20 MW 
D) 200 MW 
E) 200 W 
A) 20 kW 
B) 200 kW 
C) 20 MW 
D) 200 MW 
E) 200 W

Exam 17: Current and Resistance

The temperature coefficient of resistivity for a "perfect" ohmic material would be:

A metal wire has a resistance of 14.00 Ω at a temperature of 25.0°C.If the same wire has a resistance of 14.55 Ω at 90.0°C,what is the resistance when its temperature is −32.0°C?

A copper cable needs to carry a current of 160 A with a power loss of only 2.0 W/m.What is the required radius of the copper cable? (The resistivity of copper is 1.7 × 10−8 Ω⋅m).

A 50-W light bulb is in a socket supplied with 140 V.What is the current in the bulb?

When the voltage across a nonohmic resistor is doubled,the current through it triples.What happens to the power delivered to this resistor?

If a light bulb has half the resistance of a 110-W light bulb,what would be its wattage? Assume both bulbs are attached to the same 160-V circuit.

If a lamp has resistance of 140 Ω when it operates at 130 W,what is the applied voltage?

​A light bulb is connected to a 12-V battery.Because light bulbs are non-Ohmic,the resistance of the bulb is not constant,but increases as the bulb gets hotter.As the bulb heats up,which value remains unchanged?

Wire A and Wire B are each carrying the same current.If the diameter of Wire A is twice that of Wire B,how does the drift velocity vdA in Wire A compare to that in in Wire B?

The resistivity of a material is doubled when heated a certain amount.What happens to the resistance of a resistor made of this material when heated the same amount?

A resistor is connected to a battery with negligible internal resistance.If you replace the resistor with one that has triple the resistance,by what factor does the power dissipated in the circuit change?

A Nichrome wire has a radius of 1.3 mm and a resistivity of 1.5 × 10−6 Ω⋅m.What is the resistance per unit length of this wire?

You measure a 20-V potential difference across a 7.0-Ω resistor.What is the current flowing through it?

A tungsten wire is used to determine the melting point of indium.The resistance of the tungsten wire is 3.000 Ω at 20.0°C and increases to 4.850 Ω as the indium starts to melt.αtungsten = 4.50 × 10−3 (°C)−1.What is the melting temperature of indium?

How long is a wire made from 100 cm3 of copper if its resistance is 4.0 ohms? The resistivity of copper is 1.7 × 10-5 Ω·m.

The unit of electric current,the ampere,is equivalent to which of the following?

If a metallic wire of cross-sectional area 4.0 × 10−6 m2 carries a current of 7.0 A and has a mobile charge density of 4.24 × 1028 carriers/m3,what is the average drift velocity of the mobile charge carriers? (charge value = 1.6 × 10−19 C)

A 16-Ω platinum wire at 20°C with a temperature coefficient of resistivity of 3.9 × 10−3 (°C)−1 will have what resistance at 80°C?

An electric car is designed to run off a bank of 14.0-V batteries with total energy storage of 3.00 × 107 J.If the electric motor draws 7 000 W,what current will be delivered to the motor?

A high-voltage transmission line carries 1 000 A at 700 kV for a distance of 200 miles.If the resistance in the wire is 1 Ω/mile,what is the power loss due to resistive losses?

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Filters

A copper cable needs to carry a current of 160 A with a power loss of only 2.0 W/m.What is the required radius of the copper cable? (The resistivity of copper is 1.7 × 10−⁸ Ω⋅m).

A light bulb is connected to a 12-V battery.Because light bulbs are non-Ohmic,the resistance of the bulb is not constant,but increases as the bulb gets hotter.As the bulb heats up,which value remains unchanged?

Wire A and Wire B are each carrying the same current.If the diameter of Wire A is twice that of Wire B,how does the drift velocity v_dA in Wire A compare to that in in Wire B?

A Nichrome wire has a radius of 1.3 mm and a resistivity of 1.5 × 10−⁶ Ω⋅m.What is the resistance per unit length of this wire?

A tungsten wire is used to determine the melting point of indium.The resistance of the tungsten wire is 3.000 Ω at 20.0°C and increases to 4.850 Ω as the indium starts to melt.α_tungsten = 4.50 × 10−³ (°C)−¹.What is the melting temperature of indium?

How long is a wire made from 100 cm³ of copper if its resistance is 4.0 ohms? The resistivity of copper is 1.7 × 10^-5 Ω·m.

If a metallic wire of cross-sectional area 4.0 × 10−⁶ m² carries a current of 7.0 A and has a mobile charge density of 4.24 × 10²⁸ carriers/m³,what is the average drift velocity of the mobile charge carriers? (charge value = 1.6 × 10−¹⁹ C)

A 16-Ω platinum wire at 20°C with a temperature coefficient of resistivity of 3.9 × 10−³ (°C)−¹ will have what resistance at 80°C?

An electric car is designed to run off a bank of 14.0-V batteries with total energy storage of 3.00 × 10⁷ J.If the electric motor draws 7 000 W,what current will be delivered to the motor?