Question 1

List two conditions for producing an electric current in a circuit.

Accepted Answer

(1) must supply a potential difference
(2) must provide a continuous conducting path

Question 2

Materials in which the resistivity becomes essentially zero at very low temperatures are referred to as

Accepted Answer

A) conductors. 
B) insulators. 
C) semiconductors. 
D) superconductors. 
A) conductors. 
B) insulators. 
C) semiconductors. 
D) superconductors. D

Question 3

Consider two copper wires. One has twice the cross-sectional area of the other. How do the resistances of these two wires compare?

Accepted Answer

A) Both wires have the same resistance. 
B) The thicker wire has half the resistance of the shorter wire. 
C) The thicker wire has twice the resistance of the shorter wire. 
D) none of the given answers 
A) Both wires have the same resistance. 
B) The thicker wire has half the resistance of the shorter wire. 
C) The thicker wire has twice the resistance of the shorter wire. 
D) none of the given answers B

Question 4

A 500-W device is connected to a 120-V ac power source. What is the peak voltage across this device?

Accepted Answer

A) 4.2 V 
B) 5.9 V 
C) 120 V 
D) 150 A 
E) 170 V 
A) 4.2 V 
B) 5.9 V 
C) 120 V 
D) 150 A 
E) 170 V

Question 5

A 400-W computer (computer plus monitor) is turned on 8.0 hours per day. If electricity costs 10 cents per kWh, how much does it cost to run the computer annually?

Accepted Answer

A) $116.80 
B) $1168.00 
C) $14.60 
D) $16.80 
E) $146.00 
A) $116.80 
B) $1168.00 
C) $14.60 
D) $16.80 
E) $146.00

Question 6

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 × 10-7 Ωm 
B) 3.9 × 10-8 Ωm 
C) 4 × 10-7 Ωm 
D) 16 × 10-8 Ωm 
E) 0.25 Ω 
A) 5 × 10-7 Ωm 
B) 3.9 × 10-8 Ωm 
C) 4 × 10-7 Ωm 
D) 16 × 10-8 Ωm 
E) 0.25 Ω

Question 7

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

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/m2 
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/m2

Question 8

When a current I1 = 1.3 A passes through a wire of cross-sectional area A1 = 5 mm2 the drift velocity of the charge carriers is v1 = 2.7 × 10-5 m/s. What is the drift velocity of the charges when a current I2 = 0.5 A passes through a wire, made of the same material of cross-sectional area A2 = 3 mm2?

Accepted Answer

A) 8.4 × 10-5 m/s 
B) 6.4 × 10-5 m/s 
C) 1.7 × 10-5 m/s 
D) 3.2 × 10-5 m/s 
E) 2.1 × 10-5 m/s 
A) 8.4 × 10-5 m/s 
B) 6.4 × 10-5 m/s 
C) 1.7 × 10-5 m/s 
D) 3.2 × 10-5 m/s 
E) 2.1 × 10-5 m/s

Question 9

Outlets on a household circuit are arranged in

Accepted Answer

A) neither series or parallel. 
B) series. 
C) parallel. 
D) a combination of series and parallel. 
E) not given 
A) neither series or parallel. 
B) series. 
C) parallel. 
D) a combination of series and parallel. 
E) not given

Question 10

FIGURE 25-3  
-Electric charges flow through a wire shaped as shown in Fig. 25-3. The cross-sectional areas are A1= 4 mm2 and A2 = 1 mm2 respectively. What is the drift velocity of the electrons in the narrow section of the wire if their velocity is 0.08 m/s in the wider region?

Accepted Answer

A) 0.16 m/s 
B) 0.02 m/s 
C) 0.04 m/s 
D) 0.32 m/s 
E) 0.08 m/s 
A) 0.16 m/s 
B) 0.02 m/s 
C) 0.04 m/s 
D) 0.32 m/s 
E) 0.08 m/s

Question 11

The longer a given diameter of wire, the higher its resistance.

Accepted Answer

A) True 
 B)False

Question 12

A light bulb operating at 110 V draws 1.40 A of current. What is its resistance?

Accepted Answer

A) 12.7 Ω 
B) 78.6 Ω 
C) 109 Ω 
D) 117 Ω 
E) 154 Ω 
A) 12.7 Ω 
B) 78.6 Ω 
C) 109 Ω 
D) 117 Ω 
E) 154 Ω

Question 13

A device that produces electricity by transforming chemical energy into electrical energy is called a

Accepted Answer

A) generator. 
B) transformer. 
C) battery. 
D) superconductor. 
E) none of the given answers 
A) generator. 
B) transformer. 
C) battery. 
D) superconductor. 
E) none of the given answers

Question 14

If an all electric house uses 2400 kWh in a month, what will the amount of the bill for electricity be at a rate of 9.5 cents per kWh?

Accepted Answer

A) $23 
B) $2280 
C) $228 
D) $25,300 
E) $11.50 
A) $23 
B) $2280 
C) $228 
D) $25,300 
E) $11.50

Question 15

A current that is sinusoidal with respect to time is referred to as

Accepted Answer

A) a direct current. 
B) an alternating current. 
A) a direct current. 
B) an alternating current.

Question 16

The diameter of no. 12 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 one cubic centimeter of copper is 8.5 × 1022.)

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

Question 17

The resistance of a 100-cm wire of cross sectional area 2 × 10-6 m2 is 400 Ω. What is the resistivity of the material of this wire?

Accepted Answer

A) 0.8 × 10-4 Ωm 
B) 8 × 10-4 Ωm 
C) 0.8 × 10-5 Ωm 
D) 0.8 × 10-6 Ωm 
E) 8 × 10-6 Ωm 
A) 0.8 × 10-4 Ωm 
B) 8 × 10-4 Ωm 
C) 0.8 × 10-5 Ωm 
D) 0.8 × 10-6 Ωm 
E) 8 × 10-6 Ωm

Question 18

A 200-W light bulb is connected across 110 V. What current will flow through this bulb?

Accepted Answer

A) 0.90 A 
B) 0.36 A 
C) 0 A 
D) 0.60 A 
E) 1.8 A 
A) 0.90 A 
B) 0.36 A 
C) 0 A 
D) 0.60 A 
E) 1.8 A

Question 19

What length of copper wire (resistivity 1.68 × 10-8 Ω∙m) of diameter 0.15 mm is needed for a total resistance of 15 Ω?

Accepted Answer

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

Question 20

A 4000-Ω resistor is connected across 220 V. What current will flow?

Accepted Answer

A) 0.055 A 
B) 1.8 A 
C) 5.5 A 
D) 18 A 
E) 550 A 
A) 0.055 A 
B) 1.8 A 
C) 5.5 A 
D) 18 A 
E) 550 A

Exam 25: Electric Currents and Resistance

List two conditions for producing an electric current in a circuit.

Materials in which the resistivity becomes essentially zero at very low temperatures are referred to as

Consider two copper wires. One has twice the cross-sectional area of the other. How do the resistances of these two wires compare?

A 500-W device is connected to a 120-V ac power source. What is the peak voltage across this device?

A 400-W computer (computer plus monitor) is turned on 8.0 hours per day. If electricity costs 10 cents per kWh, how much does it cost to run the computer annually?

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

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

Outlets on a household circuit are arranged in

FIGURE 25-3 -Electric charges flow through a wire shaped as shown in Fig. 25-3. The cross-sectional areas are A1= 4 mm2 and A2 = 1 mm2 respectively. What is the drift velocity of the electrons in the narrow section of the wire if their velocity is 0.08 m/s in the wider region?

The longer a given diameter of wire, the higher its resistance.

A light bulb operating at 110 V draws 1.40 A of current. What is its resistance?

A device that produces electricity by transforming chemical energy into electrical energy is called a

If an all electric house uses 2400 kWh in a month, what will the amount of the bill for electricity be at a rate of 9.5 cents per kWh?

A current that is sinusoidal with respect to time is referred to as

The diameter of no. 12 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 one cubic centimeter of copper is 8.5 × 1022.)

The resistance of a 100-cm wire of cross sectional area 2 × 10-6 m2 is 400 Ω. What is the resistivity of the material of this wire?

A 200-W light bulb is connected across 110 V. What current will flow through this bulb?

What length of copper wire (resistivity 1.68 × 10-8 Ω∙m) of diameter 0.15 mm is needed for a total resistance of 15 Ω?

A 4000-Ω resistor is connected across 220 V. What current will flow?

Introduction, Measurement, Estimating

Describing Motion: Kinematics in One Dimension

Kinematics in Two or Three Dimensions; Vectors

Dynamics: Newtons Laws of Motion

Using Newtons Laws: Friction, Circular Motion, Drag Forces

Gravitation and Newtons6 Synthesis

Work and Energy

Conservation of Energy

Linear Momentum

Rotational Motion

Angular Momentum; General Rotation

Static Equilibrium; Elasticity and Fracture

Fluids

Oscillations

Wave Motion

Sound

Temperature, Thermal Expansion, and the Ideal Gas Law

Kinetic Theory of Gases

Heat and the First Law of Thermodynamics

Second Law of Thermodynamics

Electric Charge and Electric Field

Gausss Law

Electric Potential

Capacitance, Dielectrics, Electric Energy Storage

Dc Circuits

Magnetism

Sources of Magnetic Field

Electromagnetic Induction and Faradays Law

Inductance, Electromagnetic Oscillations, and Ac Circuits

Maxwells Equations and Electromagnetic Waves

Light: Reflection and Refraction

Lenses and Optical Instruments

The Wave Nature of Light; Interference

Diffraction and Polarization

Special Theory of Relativity

Early Quantum Theory and Models of the Atom

Quantum Mechanics

Quantum Mechanics of Atoms

Molecules and Solids

Nuclear Physics and Radioactivity

Nuclear Energy: Efects and Uses of Radiation

Elementary Particle

Astrophysics and Cosmology

Filters

FIGURE 25-3 -Electric charges flow through a wire shaped as shown in Fig. 25-3. The cross-sectional areas are A₁= 4 mm² and A₂ = 1 mm² respectively. What is the drift velocity of the electrons in the narrow section of the wire if their velocity is 0.08 m/s in the wider region?

The resistance of a 100-cm wire of cross sectional area 2 × 10^-6 m² is 400 Ω. What is the resistivity of the material of this wire?

What length of copper wire (resistivity 1.68 × 10^-⁸ Ω∙m) of diameter 0.15 mm is needed for a total resistance of 15 Ω?