Question 1

In a conductor carrying a current we expect the electron drift speed to be:

Accepted Answer

A)  much greater than the average electron speed 
B)  much less than the average electron speed 
C)  about the same as the average electron speed 
D)  less than the electron speed at low temperature and greater than the electron speed at high temperature 
E)  less than the electron speed at high temperature and greater than the electron speed at low temperature 
A)  much greater than the average electron speed 
B)  much less than the average electron speed 
C)  about the same as the average electron speed 
D)  less than the electron speed at low temperature and greater than the electron speed at high temperature 
E)  less than the electron speed at high temperature and greater than the electron speed at low temperature

Question 2

Suppose the electric company charges 10 cents per kW.h. How much does it cost to use a 125 watt lamp 4 hours a day for 30 days?

Accepted Answer

A)  $1.20 
B)  $1.50 
C)  $1.80 
D)  $7.20 
E)  none of these 
A)  $1.20 
B)  $1.50 
C)  $1.80 
D)  $7.20 
E)  none of these

Question 3

For an ohmic resistor, resistance is the proportionality constant for:

Accepted Answer

A)  potential difference and electric field 
B)  current and electric field 
C)  current and length 
D)  current and cross-sectional area 
E)  current and potential difference 
A)  potential difference and electric field 
B)  current and electric field 
C)  current and length 
D)  current and cross-sectional area 
E)  current and potential difference

Question 4

Conductivity is:

Accepted Answer

A)  the same as resistivity, it is just more convenient to use for good conductors 
B)  expressed in $\Omega$-1 
C)  equal to 1/resistance 
D)  expressed in ($\Omega$ .m)-1  
E)  not a meaningful quantity for an insulator 
A)  the same as resistivity, it is just more convenient to use for good conductors 
B)  expressed in $\Omega$-1 
C)  equal to 1/resistance 
D)  expressed in ($\Omega$ .m)-1  
E)  not a meaningful quantity for an insulator

Question 5

A certain wire has resistance R. Another wire, of the same material, has half the length and half the diameter of the first wire. The resistance of the second wire is:

Accepted Answer

A)  R/4 
B)  R/2 
C)  R 
D)  2R 
E)  4R 
A)  R/4 
B)  R/2 
C)  R 
D)  2R 
E)  4R

Question 6

You wish to triple the rate of energy dissipation in a heating device. To do this you could triple:

Accepted Answer

A)  the potential difference keeping the resistance the same 
B)  the current keeping the resistance the same 
C)  the resistance keeping the potential difference the same 
D)  the resistance keeping the current the same 
E)  both the potential difference and current 
A)  the potential difference keeping the resistance the same 
B)  the current keeping the resistance the same 
C)  the resistance keeping the potential difference the same 
D)  the resistance keeping the current the same 
E)  both the potential difference and current

Question 7

The current density is the same in two wires. Wire A has twice the free electron concentration of wire B. The drift speed of electrons in A is:

Accepted Answer

A)  twice that of electrons in B 
B)  four times that of electrons in B 
C)  half that of electrons in B 
D)  one-fourth that of electrons in B 
E)  the same as that of electrons in B 
A)  twice that of electrons in B 
B)  four times that of electrons in B 
C)  half that of electrons in B 
D)  one-fourth that of electrons in B 
E)  the same as that of electrons in B

Question 8

A certain x-ray tube requires a current of 7 mA at a voltage of 80 kV. The rate of energy dissipation (in watts) is:

Accepted Answer

A)  560 
B)  5600 
C)  26 
D)  11.4 
E)  87.5 
A)  560 
B)  5600 
C)  26 
D)  11.4 
E)  87.5

Question 9

Current has units:

Accepted Answer

A)  kilowatt·hour 
B)  coulomb/second 
C)  coulomb 
D)  volt 
E)  ohm 
A)  kilowatt·hour 
B)  coulomb/second 
C)  coulomb 
D)  volt 
E)  ohm

Exam 26: Current and Resistance

In a conductor carrying a current we expect the electron drift speed to be:

Suppose the electric company charges 10 cents per kW.h. How much does it cost to use a 125 watt lamp 4 hours a day for 30 days?

For an ohmic resistor, resistance is the proportionality constant for:

Conductivity is:

A certain wire has resistance R. Another wire, of the same material, has half the length and half the diameter of the first wire. The resistance of the second wire is:

You wish to triple the rate of energy dissipation in a heating device. To do this you could triple:

The current density is the same in two wires. Wire A has twice the free electron concentration of wire B. The drift speed of electrons in A is:

A certain x-ray tube requires a current of 7 mA at a voltage of 80 kV. The rate of energy dissipation (in watts) is:

Current has units:

Measurement

Motion Along a Straight Line

Vector

Motion in Two and Three Dimensions

Force and Motion I

Force and Motion II

Kinetic Energy and Work

Potential Energy and Conservation of Energy

Center of Mass and Linear Momentum

Rotation

Rolling, Torque, and Angular Momentum

Equilibrium and Elasticity

Gravitation

Fluids

Oscillations

Waves I

Waves II

Temperature, Heat, and the First Law of Thermodynamics

The Kinetic Theory of Gases

Entropy and the Second Law of Thermodynamics

Electric Charge

Electric Fields

Gauss Law

Electric Potential

Capacitance

Circuits

Magnetic Fields

Magnetic Fields Due to Currents

Induction and Inductance

Electromagnetic Oscillations and Alternating Current

Maxwells Equations; Magnetism of Matter

Electromagnetic Waves

Images

Interference

Diffraction

Relativity

Photons and Matter Waves

More About Matter Waves

All About Atoms

Conduction of Electricity in Solids

Nuclear Physics

Energy From the Nucleus

Quarks, Leptons, and the Big Bang

Filters