Question 1

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*W 
C) V*A 
D) V/W 
A) V/s 
B) A*W 
C) V*A 
D) V/W

Question 2

If the current in a wire is tripled, what effect does this have on the electron drift velocity in the wire?

Accepted Answer

A) It stays the same. 
B) It triples. 
C) It decreases by a factor of three. 
D) It increases by a factor of nine. 
A) It stays the same. 
B) It triples. 
C) It decreases by a factor of three. 
D) It increases by a factor of nine.

Question 3

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 3.0 * 107 J.If the electric motor draws 6 000 W in moving the car at a steady speed of 10 m/s, how far will the car go before it is "out of juice?"

Accepted Answer

A) 25 km 
B) 50 km 
C) 100 km 
D) 150 km 
A) 25 km 
B) 50 km 
C) 100 km 
D) 150 km

Question 4

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 3.0 * 107 J.If the electric motor draws 6 000 W, what current will be delivered to the motor?

Accepted Answer

A) 500 A 
B) 400 A 
C) 200 A 
D) 100 A 
A) 500 A 
B) 400 A 
C) 200 A 
D) 100 A

Question 5

If a lamp has a resistance of 120 W when it operates at 100 W, what current does it carry?

Accepted Answer

A) 2.10 A 
B) 1.2 A 
C) 0.91 A 
D) 0.83 A 
A) 2.10 A 
B) 1.2 A 
C) 0.91 A 
D) 0.83 A

Question 6

A light bulb, sold as long-lasting, is rated 100 W at 130 V.The "increased" lifetime comes from using it at 120 V.Assuming negligible change in resistance at the different voltage, what is its power consumption at 120 V?

Accepted Answer

A) 85 W 
B) 92 W 
C) 100 W 
D) 108 W 
A) 85 W 
B) 92 W 
C) 100 W 
D) 108 W

Question 7

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 8

A Nichrome wire has a radius of 0.50 mm and a resistivity of 1.5 * 10-6 W*m.If the wire carries a current of 0.50 A, what is the potential difference per unit length along this wire?

Accepted Answer

A) 0.003 V/m 
B) 0.95 V/m 
C) 1.6 V/m 
D) 1.9 V/m 
A) 0.003 V/m 
B) 0.95 V/m 
C) 1.6 V/m 
D) 1.9 V/m

Question 9

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 10

The resistance of a platinum wire is to be calibrated for low-temperature work.A platinum wire with resistance 1.000 W at 20$\degree$C is immersed in liquid nitrogen at 77 K (-196$\degree$C).If the temperature response of the platinum wire is linear, what is the expected resistance of the platinum wire at -196$\degree$C? [aplatinum = 3.92 * 10-3 ($\degree$C)-1].

Accepted Answer

A) 0.153 W 
B) 0.232 W 
C) 1.768 W 
D) 1.847 W 
A) 0.153 W 
B) 0.232 W 
C) 1.768 W 
D) 1.847 W

Question 11

When an electric current exists within a conducting wire, which of the following statements describes the condition of any accompanying electric field?

Accepted Answer

A) must be zero 
B) must be parallel to current flow 
C) must be anti-parallel (opposite direction) to current flow 
D) must be perpendicular to current flow 
A) must be zero 
B) must be parallel to current flow 
C) must be anti-parallel (opposite direction) to current flow 
D) must be perpendicular to current flow

Question 12

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

Accepted Answer

A) V*W 
B) V/W 
C) W*m 
D) V/s 
A) V*W 
B) V/W 
C) W*m 
D) V/s

Question 13

If electrical energy costs 5.5 cents per kWh, what does it cost to heat 200 kg water from 15$\degree$C to 80$\degree$C? (The specific heat of water = 103 cal/kg*$\degree$C and 1.0 cal = 4.186 J.)

Accepted Answer

A) 48 cents 
B) 83 cents 
C) 16 cents 
D) 80 cents 
A) 48 cents 
B) 83 cents 
C) 16 cents 
D) 80 cents

Question 14

An 8.00-W resistor is dissipating 100 watts. What are the current through it and the difference of potential across it?

Accepted Answer

A) 12.5 A, 28.3 V 
B) 3.54 A, 12.5 V 
C) 3.54 A, 28.3 V 
D) 28.3 A, 3.54 V 
A) 12.5 A, 28.3 V 
B) 3.54 A, 12.5 V 
C) 3.54 A, 28.3 V 
D) 28.3 A, 3.54 V

Question 15

If a 9.0-V battery, with negligible internal resistance, and an 18-W resistor are connected in series, what is the amount of electrical energy transformed to heat per coulomb of charge that flows through the circuit?

Accepted Answer

A) 0.50 J 
B) 3.0 J 
C) 9.0 J 
D) 72 J 
A) 0.50 J 
B) 3.0 J 
C) 9.0 J 
D) 72 J

Question 16

When current is flowing in a superconductor, which statement is not true?

Accepted Answer

A) A battery is needed to keep the current going. 
B) Electrical charges are moving. 
C) The resistance is zero. 
D) No power is given off in the form of heat. 
A) A battery is needed to keep the current going. 
B) Electrical charges are moving. 
C) The resistance is zero. 
D) No power is given off in the form of heat.

Question 17

How long is a wire made from 100 cm3 of copper if its resistance is 8.5 ohms? The resistivity of copper is 1.7 * 10-5 W·m.

Accepted Answer

A) 7.1 m 
B) 1.7 * 102 m 
C) 2.2 * 102 m 
D) 3.0 * 103 m 
A) 7.1 m 
B) 1.7 * 102 m 
C) 2.2 * 102 m 
D) 3.0 * 103 m

Question 18

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

Accepted Answer

A) 0.50 
B) 0.25 
C) 4.0 
D) 2.0 
A) 0.50 
B) 0.25 
C) 4.0 
D) 2.0

Exam 17: Current and Resistance

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

If the current in a wire is tripled, what effect does this have on the electron drift velocity in the wire?

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 3.0 * 107 J.If the electric motor draws 6 000 W in moving the car at a steady speed of 10 m/s, how far will the car go before it is "out of juice?"

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 3.0 * 107 J.If the electric motor draws 6 000 W, what current will be delivered to the motor?

If a lamp has a resistance of 120 W when it operates at 100 W, what current does it carry?

A light bulb, sold as long-lasting, is rated 100 W at 130 V.The "increased" lifetime comes from using it at 120 V.Assuming negligible change in resistance at the different voltage, what is its power consumption at 120 V?

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

A Nichrome wire has a radius of 0.50 mm and a resistivity of 1.5 * 10-6 W*m.If the wire carries a current of 0.50 A, what is the potential difference per unit length along this wire?

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

When an electric current exists within a conducting wire, which of the following statements describes the condition of any accompanying electric field?

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

If electrical energy costs 5.5 cents per kWh, what does it cost to heat 200 kg water from 15 °\degree° C to 80 °\degree° C? (The specific heat of water = 103 cal/kg* °\degree° C and 1.0 cal = 4.186 J.)

An 8.00-W resistor is dissipating 100 watts. What are the current through it and the difference of potential across it?

If a 9.0-V battery, with negligible internal resistance, and an 18-W resistor are connected in series, what is the amount of electrical energy transformed to heat per coulomb of charge that flows through the circuit?

When current is flowing in a superconductor, which statement is not true?

How long is a wire made from 100 cm3 of copper if its resistance is 8.5 ohms? The resistivity of copper is 1.7 * 10-5 W·m.

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

Introduction

Motion in One Dimension

Vectors and Two-Dimensional Motion

The Laws of Motion

Energy

Momentum and Collisions

Rotational Motion and the Law of Gravity

Rotational Equilibrium and Rotational Dynamics

Solids and Fluids

Thermal Physics

Energy in Thermal Processes

The Laws of Thermodynamics

Vibrations and Waves

Sound

Electric Forces and Electric Fields

Electrical Energy and Capacitance

Direct-Current Circuits

Magnetism

Induced Voltages and Inductance

Alternating Current Circuits and Electromagnetic Waves

Reflection and Refraction of Light

Mirrors and Lenses

Wave Optics

Optical Instruments

Relativity

Quantum Physics

Atomic Physics

Nuclear Physics

Nuclear Energy and Elementary Particles

Filters

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 3.0 * 10⁷ J.If the electric motor draws 6 000 W in moving the car at a steady speed of 10 m/s, how far will the car go before it is "out of juice?"

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 3.0 * 10⁷J.If the electric motor draws 6 000 W, what current will be delivered to the motor?

A Nichrome wire has a radius of 0.50 mm and a resistivity of 1.5 * 10^-6 W*m.If the wire carries a current of 0.50 A, what is the potential difference per unit length along this wire?

If electrical energy costs 5.5 cents per kWh, what does it cost to heat 200 kg water from 15 $\degree$ C to 80 $\degree$ C? (The specific heat of water = 10³ cal/kg* $\degree$ C and 1.0 cal = 4.186 J.)

How long is a wire made from 100 cm³ of copper if its resistance is 8.5 ohms? The resistivity of copper is 1.7 * 10^-5 W·m.