Question 1

A student kept her 60-watt, 120-volt study lamp turned on from 2:00 PM until 2:00 AM. How many coulombs of charge went through it?

Accepted Answer

A)  150 
B)  3,600 
C)  7,200 
D)  18,000 
E)  21,600 
A)  150 
B)  3,600 
C)  7,200 
D)  18,000 
E)  21,600 E

Question 2

A certain sample carries a current of 4 A when the potential difference is 2 V and a current of 10 A when the potential difference is 4 V. This sample:

Accepted Answer

A)  obeys Ohm's law 
B)  has a resistance of 0.5$\Omega$at 1 V 
C)  has a resistance of 2.5$\Omega$at 2 V 
D)  has a resistance of 25 $\Omega$ at 2 V 
E)  does not have a resistance 
A)  obeys Ohm's law 
B)  has a resistance of 0.5$\Omega$at 1 V 
C)  has a resistance of 2.5$\Omega$at 2 V 
D)  has a resistance of 25 $\Omega$ at 2 V 
E)  does not have a resistance B

Question 3

Of the following the copper conductor that has the least resistance is:

Accepted Answer

A)  thin, long and hot 
B)  thick, short and cool 
C)  thick, long and hot 
D)  thin, short and cool 
E)  thin, short and hot 
A)  thin, long and hot 
B)  thick, short and cool 
C)  thick, long and hot 
D)  thin, short and cool 
E)  thin, short and hot B

Question 4

An ordinary light bulb is marked "60 watt, 120 volt". Its resistance is:

Accepted Answer

A)  60 $\Omega$ 
B)  120$\Omega$ 
C)  180 $\Omega$ 
D)  240 $\Omega$ 
E)  15$\Omega$ 
A)  60 $\Omega$ 
B)  120$\Omega$ 
C)  180 $\Omega$ 
D)  240 $\Omega$ 
E)  15$\Omega$

Question 5

Two conductors are made of the same material and have the same length. Conductor A is a solid wire of diameter 1 m. Conductor B is a hollow tube of inside diameter 1 m and outside diameter 2 m. The ratio of their resistance, RA/RB, is:

Accepted Answer

A)  1 
B)    
C)  2 
D)  3 
E)  4 
A)  1 
B)    
C)  2 
D)  3 
E)  4

Question 6

Five cylindrical wires are made of the same material. Their lengths and radii are   Rank the wires according to their resistances, least to greatest.

Accepted Answer

A)  1, 2, 3, 4, 5 
B)  5, 4, 3, 2, 1 
C)  1 and 2 tie, then 5, 3, 4 
D)  1, 3, 4, 2, 5 
E)  1, 2, 4, 3, 5 
A)  1, 2, 3, 4, 5 
B)  5, 4, 3, 2, 1 
C)  1 and 2 tie, then 5, 3, 4 
D)  1, 3, 4, 2, 5 
E)  1, 2, 4, 3, 5

Question 7

If   is the current density and   is a vector element of area then the integral   over an area represents:

Accepted Answer

A)  the electric flux through the area 
B)  the average current density at the position of the area 
C)  the resistance of the area 
D)  the resistivity of the area 
E)  the current through the area 
A)  the electric flux through the area 
B)  the average current density at the position of the area 
C)  the resistance of the area 
D)  the resistivity of the area 
E)  the current through the area

Question 8

A 10-ohm resistor has a constant current. If 1200 C of charge flow through it in 4 minutes what is the value of the current?

Accepted Answer

A)  3.0 A 
B)  5.0 A 
C)  11 A 
D)  15 A 
E)  20 A 
A)  3.0 A 
B)  5.0 A 
C)  11 A 
D)  15 A 
E)  20 A

Question 9

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 10

The units of resistivity are:

Accepted Answer

A)  ohm 
B)  ohm·meter 
C)  ohm/meter 
D)  ohm/meter2 
E)  none of these 
A)  ohm 
B)  ohm·meter 
C)  ohm/meter 
D)  ohm/meter2 
E)  none of these

Question 11

Which of the following graphs best represents the current-voltage relationship for a device that obeys Ohm's law?

Accepted Answer

A)  I 
B)  II 
C)  III 
D)  IV 
E)  V 
A)  I 
B)  II 
C)  III 
D)  IV 
E)  V

Question 12

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 13

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 14

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 15

It is better to send 10,000 kW of electric power long distances at 10,000 V rather than at 220 V because:

Accepted Answer

A)  there is less heating in the transmission wires 
B)  the resistance of the wires is less at high voltages 
C)  more current is transmitted at high voltages 
D)  the insulation is more effective at high voltages 
E)  the iR drop along the wires is greater at high voltage 
A)  there is less heating in the transmission wires 
B)  the resistance of the wires is less at high voltages 
C)  more current is transmitted at high voltages 
D)  the insulation is more effective at high voltages 
E)  the iR drop along the wires is greater at high voltage

Question 16

Conduction electrons move to the right in a certain wire. This indicates that:

Accepted Answer

A)  the current density and electric field both point right 
B)  the current density and electric field both point left 
C)  the current density points right and the electric field points left 
D)  the current density points left and the electric field points right 
E)  the current density points left but the direction of the electric field is unknown 
A)  the current density and electric field both point right 
B)  the current density and electric field both point left 
C)  the current density points right and the electric field points left 
D)  the current density points left and the electric field points right 
E)  the current density points left but the direction of the electric field is unknown

Question 17

Copper contains 8.4 * 1028 free electrons/m3. A copper wire of cross-sectional area 7.4* 10-7 m2 carries a current of 1 A. The electron drift speed is approximately:

Accepted Answer

A)  3 * 108 m/s 
B)  103 m/s 
C)  1 m/s 
D)  10-4 m/s 
E)  10-23 m/s 
A)  3 * 108 m/s 
B)  103 m/s 
C)  1 m/s 
D)  10-4 m/s 
E)  10-23 m/s

Question 18

If the potential difference across a resistor is doubled:

Accepted Answer

A)  only the current is doubled 
B)  only the current is halved 
C)  only the resistance is doubled 
D)  only the resistance is halved 
E)  both the current and resistance are doubled 
A)  only the current is doubled 
B)  only the current is halved 
C)  only the resistance is doubled 
D)  only the resistance is halved 
E)  both the current and resistance are doubled

Question 19

For an ohmic substance, the resistivity depends on:

Accepted Answer

A)  the electric field 
B)  the potential difference 
C)  the current density 
D)  the electron mean free time 
E)  the cross-sectionalarea of the sample 
A)  the electric field 
B)  the potential difference 
C)  the current density 
D)  the electron mean free time 
E)  the cross-sectionalarea of the sample

Question 20

Two wires made of different materials have the same uniform current density. They carry the same current only if:

Accepted Answer

A)  their lengths are the same 
B)  their cross-sectional areas are the same 
C)  both their lengths and cross-sectional areas are the same 
D)  the potential differences across them are the same 
E)  the electric fields in them are the same 
A)  their lengths are the same 
B)  their cross-sectional areas are the same 
C)  both their lengths and cross-sectional areas are the same 
D)  the potential differences across them are the same 
E)  the electric fields in them are the same

Exam 26: Current and Resistance

A student kept her 60-watt, 120-volt study lamp turned on from 2:00 PM until 2:00 AM. How many coulombs of charge went through it?

A certain sample carries a current of 4 A when the potential difference is 2 V and a current of 10 A when the potential difference is 4 V. This sample:

Of the following the copper conductor that has the least resistance is:

An ordinary light bulb is marked "60 watt, 120 volt". Its resistance is:

Two conductors are made of the same material and have the same length. Conductor A is a solid wire of diameter 1 m. Conductor B is a hollow tube of inside diameter 1 m and outside diameter 2 m. The ratio of their resistance, RA/RB, is:

Five cylindrical wires are made of the same material. Their lengths and radii are Rank the wires according to their resistances, least to greatest.

If is the current density and is a vector element of area then the integral over an area represents:

A 10-ohm resistor has a constant current. If 1200 C of charge flow through it in 4 minutes what is the value of the current?

Conductivity is:

The units of resistivity are:

Which of the following graphs best represents the current-voltage relationship for a device that obeys Ohm's law?

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

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?

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

It is better to send 10,000 kW of electric power long distances at 10,000 V rather than at 220 V because:

Conduction electrons move to the right in a certain wire. This indicates that:

Copper contains 8.4 * 1028 free electrons/m3. A copper wire of cross-sectional area 7.4* 10-7 m2 carries a current of 1 A. The electron drift speed is approximately:

If the potential difference across a resistor is doubled:

For an ohmic substance, the resistivity depends on:

Two wires made of different materials have the same uniform current density. They carry the same current only if:

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

Two conductors are made of the same material and have the same length. Conductor A is a solid wire of diameter 1 m. Conductor B is a hollow tube of inside diameter 1 m and outside diameter 2 m. The ratio of their resistance, R_A/R_B, is:

Copper contains 8.4 * 10²⁸ free electrons/m³. A copper wire of cross-sectional area 7.4* 10^-⁷ m² carries a current of 1 A. The electron drift speed is approximately: