Question 1

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 2

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 3

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 4

A car battery is rated at 80 A F. h. An ampere-hour is a unit of:

Accepted Answer

A)  power 
B)  energy 
C)  current 
D)  charge 
E)  force 
A)  power 
B)  energy 
C)  current 
D)  charge 
E)  force

Question 5

The resistance of a rod does NOT depend on:

Accepted Answer

A)  its temperature 
B)  its material 
C)  its length 
D)  its conductivity 
E)  shape of its (fixed) cross-sectional area 
A)  its temperature 
B)  its material 
C)  its length 
D)  its conductivity 
E)  shape of its (fixed) cross-sectional area

Question 6

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

Question 7

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 8

A wire with a length of 150 m and a radius of 0.15 m carries a current with a uniform current density of 2.8 *107 A/m2. The current is:

Accepted Answer

A)  0.63 A2 
B)  2.0 A 
C)  5.9 A2 
D)  296 A 
E)  400 A2 
A)  0.63 A2 
B)  2.0 A 
C)  5.9 A2 
D)  296 A 
E)  400 A2

Question 9

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

Question 10

A current of 0.3 A is passed through a lamp for 2 minutes using a 6 V power supply. The energy dissipated by this lamp during the 2 minutes is:

Accepted Answer

A)  1.8 J 
B)  12 J 
C)  20 J 
D)  36 J 
E)  216 J 
A)  1.8 J 
B)  12 J 
C)  20 J 
D)  36 J 
E)  216 J

Question 11

For an ohmic substance, the electron drift velocity is proportional to:

Accepted Answer

A)  the cross-sectional area of the sample 
B)  the length of the sample 
C)  the mass of an electron 
D)  the electric field in the sample 
E)  none of the above 
A)  the cross-sectional area of the sample 
B)  the length of the sample 
C)  the mass of an electron 
D)  the electric field in the sample 
E)  none of the above

Question 12

Which one of the following quantities is correctly matched to its unit?

Accepted Answer

A)  power - kW·h 
B)  energy - kW 
C)  potential difference - J/C 
D)  current - A/s 
E)  resistance - V/C 
A)  power - kW·h 
B)  energy - kW 
C)  potential difference - J/C 
D)  current - A/s 
E)  resistance - V/C

Question 13

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 14

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 15

A nichrome wire is 1 m long and 1 *10-6 m2 in cross-sectional area. When connected to a potential difference of 2 V, a current of 4 A exists in the wire. The resistivity of this nichrome is:

Accepted Answer

A)  10-7 $\Omega$ . m 
B)  2 * 10-7 $\Omega$ . m 
C)  4* 10-7 $\Omega$ . m 
D)  5 * 10-7 $\Omega$ .m 
E)  8 * 10-7 $\Omega$ . m 
A)  10-7 $\Omega$ . m 
B)  2 * 10-7 $\Omega$ . m 
C)  4* 10-7 $\Omega$ . m 
D)  5 * 10-7 $\Omega$ .m 
E)  8 * 10-7 $\Omega$ . m

Question 16

Two substances are identical except that the electron mean free time for substance A is twice the electron mean free time for substance B. If the same electric field exists in both substances the electron drift speed in A is:

Accepted Answer

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

Question 17

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 18

The rate at which electrical energy is used may be measured in:

Accepted Answer

A)  watt/second 
B)  watt·second 
C)  watt 
D)  joule·second 
E)  kilowatt·hour 
A)  watt/second 
B)  watt·second 
C)  watt 
D)  joule·second 
E)  kilowatt·hour

Question 19

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 20

A cylindrical copper rod has resistance R. It is reformed to twice its original length with no change of volume. Its new resistance is:

Accepted Answer

A)  R 
B)  2R 
C)  4R 
D)  8R 
E)  R/2 
A)  R 
B)  2R 
C)  4R 
D)  8R 
E)  R/2

Exam 26: Current and Resistance

If the potential difference across a resistor is doubled:

For an ohmic substance, the resistivity depends on:

The units of resistivity are:

A car battery is rated at 80 A F. h. An ampere-hour is a unit of:

The resistance of a rod does NOT depend on:

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

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:

A wire with a length of 150 m and a radius of 0.15 m carries a current with a uniform current density of 2.8 *107 A/m2. The current is:

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:

A current of 0.3 A is passed through a lamp for 2 minutes using a 6 V power supply. The energy dissipated by this lamp during the 2 minutes is:

For an ohmic substance, the electron drift velocity is proportional to:

Which one of the following quantities is correctly matched to its unit?

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

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

A nichrome wire is 1 m long and 1 *10-6 m2 in cross-sectional area. When connected to a potential difference of 2 V, a current of 4 A exists in the wire. The resistivity of this nichrome is:

Two substances are identical except that the electron mean free time for substance A is twice the electron mean free time for substance B. If the same electric field exists in both substances the electron drift speed in A is:

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

The rate at which electrical energy is used may be measured in:

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

A cylindrical copper rod has resistance R. It is reformed to twice its original length with no change of volume. Its new resistance is:

Measurement

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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

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The Kinetic Theory of Gases

Entropy and the Second Law of Thermodynamics

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Nuclear Physics

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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:

A wire with a length of 150 m and a radius of 0.15 m carries a current with a uniform current density of 2.8 *10⁷A/m². The current is:

A nichrome wire is 1 m long and 1 *10^-⁶ m² in cross-sectional area. When connected to a potential difference of 2 V, a current of 4 A exists in the wire. The resistivity of this nichrome is: