Question 1

A high-voltage transmission line carries 1,000 A at 600,000 V.What is the power carried by the line?

Accepted Answer

A)  600 MW 
B)  350 MW 
C)  100 MW 
D)  60 MW 
E)  ​167 MW 
A)  600 MW 
B)  350 MW 
C)  100 MW 
D)  60 MW 
E)  ​167 MW

Question 2

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

Accepted Answer

A)  0.25 
B)  0.06 
C)  4 
D)  16 
E)  ​2 
A)  0.25 
B)  0.06 
C)  4 
D)  16 
E)  ​2

Question 3

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 4

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 2.1 × 107 J.If the electric motor draws 4,200 W in moving the car at a steady speed of 15 m/s,how far will the car go before it is "out of juice?"
​

Accepted Answer

A)  38 km 
B)  75 km 
C)  150 km 
D)  113 km 
E)  ​19 km 
A)  38 km 
B)  75 km 
C)  150 km 
D)  113 km 
E)  ​19 km

Question 5

The unit of electric resistance,the ohm,is equivalent to which of the following?

Accepted Answer

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

Question 6

Consider some material that has been cooled until it has become a superconductor.If it is cooled even further its resistance will:

Accepted Answer

A)  increase. 
B)  decrease. 
C)  stay constant and non-zero. 
D)  None of the above. 
A)  increase. 
B)  decrease. 
C)  stay constant and non-zero. 
D)  None of the above.

Question 7

The heating coil of a hot water heater has a resistance of 25 Ω and operates at 220 V.How long a time is required to raise the temperature of 150kg of water from 25°C to 85°C? (The specific heat for water = 103 cal/kg⋅°C and 1.0 cal = 4.186 J).

Accepted Answer

A)  1.9 h 
B)  7.7 h 
C)  2.3 h 
D)  5.4 h 
E)  ​0.9 h 
A)  1.9 h 
B)  7.7 h 
C)  2.3 h 
D)  5.4 h 
E)  ​0.9 h

Question 8

A Nichrome wire has a radius of 0.3 mm and a resistivity of 1.5 × 10−6 Ω⋅m.If the wire carries a current of 0.7 A,what is the potential difference per unit length along this wire?

Accepted Answer

A)  0.3 V/m 
B)  3.7 V/m 
C)  1.1 V/m 
D)  0.1 V/m 
E)  ​36.6 V/m 
A)  0.3 V/m 
B)  3.7 V/m 
C)  1.1 V/m 
D)  0.1 V/m 
E)  ​36.6 V/m

Question 9

If a light bulb has half the resistance of a 70-W lightbulb,what would be its wattage? Assume both bulbs are attached to the same 130-V circuit.

Accepted Answer

A)  140 W 
B)  35 W 
C)  18 W 
D)  210 W 
E)  ​More information is needed. 
A)  140 W 
B)  35 W 
C)  18 W 
D)  210 W 
E)  ​More information is needed.

Question 10

Suppose that a voltage surge produces 160 V for a moment in a 140-V line.What will temporarily be the output of a 100-W light bulb assuming its resistance does not change?
​

Accepted Answer

A)  105 W 
B)  85 W 
C)  118 W 
D)  131 W 
E)  ​66 W 
A)  105 W 
B)  85 W 
C)  118 W 
D)  131 W 
E)  ​66 W

Question 11

A metallic conductor has a resistivity of 11 × 10−6 Ω⋅m.What is the resistance of a piece that is 27 m long and has a uniform cross sectional area of 5 × 10−6 m2?

Accepted Answer

A)  0.1 Ω 
B)  59.4 Ω 
C)  12.3 Ω 
D)  2 Ω 
E)  ​1,485 Ω 
A)  0.1 Ω 
B)  59.4 Ω 
C)  12.3 Ω 
D)  2 Ω 
E)  ​1,485 Ω

Question 12

If a certain resistor obeys Ohm's law,its resistance will change:

Accepted Answer

A)  as the voltage across the resistor changes. 
B)  as the current through the resistor changes. 
C)  as the energy given off by the electrons in their collisions changes. 
D)  none of the above,since resistance is a constant for the given resistor. 
A)  as the voltage across the resistor changes. 
B)  as the current through the resistor changes. 
C)  as the energy given off by the electrons in their collisions changes. 
D)  none of the above,since resistance is a constant for the given resistor.

Question 13

A high voltage transmission line of diameter 1 cm and length 150 km carries a steady current of 1,000 A.If the conductor is copper with a free charge density of 8 × 1028 electrons/m3,how long does it take one electron to travel the full length of the cable? (e = 1.6 × 10−19 C)
​

Accepted Answer

A)  1.5 × 102 s 
B)  1.5 × 104 s 
C)  1.5 × 106 s 
D)  1.5 × 108 s 
E)  1.5 × 10-10 s 
A)  1.5 × 102 s 
B)  1.5 × 104 s 
C)  1.5 × 106 s 
D)  1.5 × 108 s 
E)  1.5 × 10-10 s

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°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

The resistance of a platinum wire is to be calibrated for low-temperature work.A platinum wire with resistance 3 Ω at 27°C is immersed in liquid nitrogen at 75 K (−198°C).If the temperature response of the platinum wire is linear,what is the expected resistance of the platinum wire at −198°C? [αplatinum = 3.92 × 10−3 (°C)−1].

Accepted Answer

A)  0.354 Ω 
B)  5.011 Ω 
C)  5.646 Ω 
D)  25.424 Ω 
E)  ​0.989 Ω 
A)  0.354 Ω 
B)  5.011 Ω 
C)  5.646 Ω 
D)  25.424 Ω 
E)  ​0.989 Ω

Question 16

The unit for rate of energy transformation,the watt,in an electric circuit is equivalent to which of the following?

Accepted Answer

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

Question 17

How long is a wire made from 50 cm3 of copper if its resistance is 8 ohms? The resistivity of copper is 1.7 × 10-5 Ω·m.

Accepted Answer

A)  4.9 m 
B)  1.7 × 102 m 
C)  1.6 × 102 m 
D)  1.5 × 103 m 
E)  ​23.5 m 
A)  4.9 m 
B)  1.7 × 102 m 
C)  1.6 × 102 m 
D)  1.5 × 103 m 
E)  ​23.5 m

Question 18

Two wires with the same resistance have the same diameter but different lengths.If wire 1 has length L1 and wire 2 has length L2,how do L1 and L2 compare if wire 1 is made from copper and wire 2 is made from aluminum? The resistivity of copper is 1.7 × 10-5 Ω·m and the resistivity of aluminum is 2.82 × 10-5 Ω·m.

Accepted Answer

A)  L1 = 1.7 L2 
B)  L1 = 0.60 L2 
C)  L1 = 2.8 L2 
D)  L1 = 0.36 L2 
A)  L1 = 1.7 L2 
B)  L1 = 0.60 L2 
C)  L1 = 2.8 L2 
D)  L1 = 0.36 L2

Question 19

A light bulb,sold as long-lasting,is rated 95 W at 145 V.The "increased" lifetime comes from using it at 105 V.Assuming negligible change in resistance at the different voltage,what is its power consumption at 105 V?

Accepted Answer

A)  50 W 
B)  181 W 
C)  177 W 
D)  45 W 
E)  ​119 W 
A)  50 W 
B)  181 W 
C)  177 W 
D)  45 W 
E)  ​119 W

Question 20

Which process will double the power given off by a resistor?

Accepted Answer

A)  doubling the current while doubling the resistance 
B)  doubling the current by making a resistance half as big 
C)  doubling the current by doubling the voltage 
D)  doubling the current while making the voltage half as big 
A)  doubling the current while doubling the resistance 
B)  doubling the current by making a resistance half as big 
C)  doubling the current by doubling the voltage 
D)  doubling the current while making the voltage half as big

Exam 17: Current and Resistance Electric Current

A high-voltage transmission line carries 1,000 A at 600,000 V.What is the power carried by the line?

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

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

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 2.1 × 107 J.If the electric motor draws 4,200 W in moving the car at a steady speed of 15 m/s,how far will the car go before it is "out of juice?" ​

The unit of electric resistance,the ohm,is equivalent to which of the following?

Consider some material that has been cooled until it has become a superconductor.If it is cooled even further its resistance will:

The heating coil of a hot water heater has a resistance of 25 Ω and operates at 220 V.How long a time is required to raise the temperature of 150kg of water from 25°C to 85°C? (The specific heat for water = 103 cal/kg⋅°C and 1.0 cal = 4.186 J).

A Nichrome wire has a radius of 0.3 mm and a resistivity of 1.5 × 10−6 Ω⋅m.If the wire carries a current of 0.7 A,what is the potential difference per unit length along this wire?

If a light bulb has half the resistance of a 70-W lightbulb,what would be its wattage? Assume both bulbs are attached to the same 130-V circuit.

Suppose that a voltage surge produces 160 V for a moment in a 140-V line.What will temporarily be the output of a 100-W light bulb assuming its resistance does not change? ​

A metallic conductor has a resistivity of 11 × 10−6 Ω⋅m.What is the resistance of a piece that is 27 m long and has a uniform cross sectional area of 5 × 10−6 m2?

If a certain resistor obeys Ohm's law,its resistance will change:

A high voltage transmission line of diameter 1 cm and length 150 km carries a steady current of 1,000 A.If the conductor is copper with a free charge density of 8 × 1028 electrons/m3,how long does it take one electron to travel the full length of the cable? (e = 1.6 × 10−19 C) ​

A tungsten wire is used to determine the melting point of indium.The resistance of the tungsten wire is 3.000 Ω at 20°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?

The unit for rate of energy transformation,the watt,in an electric circuit is equivalent to which of the following?

How long is a wire made from 50 cm3 of copper if its resistance is 8 ohms? The resistivity of copper is 1.7 × 10-5 Ω·m.

A light bulb,sold as long-lasting,is rated 95 W at 145 V.The "increased" lifetime comes from using it at 105 V.Assuming negligible change in resistance at the different voltage,what is its power consumption at 105 V?

Which process will double the power given off by a resistor?

Introduction

Introduction: Part A

Motion in One Dimension

Motion in One Dimension: Part A

Vectors and Two-Dimensional Motion

Vectors and Two-Dimensional Motion: Part A

The Laws of Motion

The Laws of Motion: Part A

Energy

Energy: Part A

Momentum and Collisions

Momentum and Collisions: Part A

Rotational Motion and the Law of Gravity

Rotational Motion and the Law of Gravity: Part A

Rotational Equilibrium and Rotational Dynamics

Rotational Equilibrium and Rotational Dynamics: Part A

Solids and Fluids

Solids and Fluids: Part A

Thermal Physics

Thermal Physics: Part A

Energy in Thermal Processes Heat and Internal Energy

Energy in Thermal Processes Heat and Internal Energy: Part A

The Laws of Thermodynamics Work in Thermodynamic Processes

The Laws of Thermodynamics Work in Thermodynamic Processes: Part A

Vibrations and Waves

Vibrations and Waves: Part A

Sound

Sound: Part A

Electric Forces and Electric Fields

Electric Forces and Electric Fields: Part A

Electrical Energy and Capacitance

Electrical Energy and Capacitance: Part A

Current and Resistance Electric Current: Part A

Direct-Current Circuits Sources of EMF

Direct-Current Circuits Sources of EMF: Part A

Magnetism Magnets

Magnetism Magnets: Part A

Induced Voltages and Inductance

Induced Voltages and Inductance: Part A

Alternating-Current Circuits and Electromagnetic Waves

Alternating-Current Circuits and Electromagnetic Waves: Part A

Reflection and Refraction of Light

Reflection and Refraction of Light: Part A

Mirrors and Lenses

Mirrors and Lenses: Part A

Wave Optics

Wave Optics: Part A

Optical Instruments

Optical Instruments: Part A

Relativity

Relativity: Part A

Quantum Physics Blackbody Radiation and Plancks Hypothesis

Quantum Physics Blackbody Radiation and Plancks Hypothesis: Part A

Atomic Physics

Atomic Physics: Part A

Nuclear Physics

Nuclear Physics: Part A

Nuclear Energy and Elementary Particles

Nuclear Energy and Elementary Particles: Part A

Particle Collisions, Mediating Photons, and Quark Structures: Exploring the Fundamentals of Physics

Filters

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 2.1 × 10⁷ J.If the electric motor draws 4,200 W in moving the car at a steady speed of 15 m/s,how far will the car go before it is "out of juice?"

The heating coil of a hot water heater has a resistance of 25 Ω and operates at 220 V.How long a time is required to raise the temperature of 150kg of water from 25°C to 85°C? (The specific heat for water = 10³ cal/kg⋅°C and 1.0 cal = 4.186 J).

A Nichrome wire has a radius of 0.3 mm and a resistivity of 1.5 × 10−⁶ Ω⋅m.If the wire carries a current of 0.7 A,what is the potential difference per unit length along this wire?

Suppose that a voltage surge produces 160 V for a moment in a 140-V line.What will temporarily be the output of a 100-W light bulb assuming its resistance does not change?

A metallic conductor has a resistivity of 11 × 10−⁶ Ω⋅m.What is the resistance of a piece that is 27 m long and has a uniform cross sectional area of 5 × 10−⁶ m²?

A high voltage transmission line of diameter 1 cm and length 150 km carries a steady current of 1,000 A.If the conductor is copper with a free charge density of 8 × 10²⁸ electrons/m³,how long does it take one electron to travel the full length of the cable? (e = 1.6 × 10−¹⁹ C)

A tungsten wire is used to determine the melting point of indium.The resistance of the tungsten wire is 3.000 Ω at 20°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 50 cm³ of copper if its resistance is 8 ohms? The resistivity of copper is 1.7 × 10^-5 Ω·m.