Question 1

For a cylindrical resistor made of ohmic material, the resistance does NOT depend on:

Accepted Answer

A)  the current 
B)  the length 
C)  the cross-sectional area 
D)  the resistivity 
E)  the electron drift velocity 
A)  the current 
B)  the length 
C)  the cross-sectional area 
D)  the resistivity 
E)  the electron drift velocity A

Question 2

An certain resistor dissipates 0.5 W when connected to a 3 V potential difference. When connected to a 1 V potential difference, this resistor will dissipate:

Accepted Answer

A)  0.5 W 
B)  0.167 W 
C)  1.5 W 
D)  0.056 W 
E)  none of these 
A)  0.5 W 
B)  0.167 W 
C)  1.5 W 
D)  0.056 W 
E)  none of these D

Question 3

A 60-watt light bulb carries a current of 0.5 ampere. The total charge passing through it in one hour is:

Accepted Answer

A)  120 C 
B)  3600 C 
C)  3000 C 
D)  2400 C 
E)  1800 C 
A)  120 C 
B)  3600 C 
C)  3000 C 
D)  2400 C 
E)  1800 C E

Question 4

For an ohmic substance the resistivity is the proportionality constant for:

Accepted Answer

A)  current and potential difference 
B)  current and electric field 
C)  current density and potential difference 
D)  current density and electric field 
E)  potential difference and electric field 
A)  current and potential difference 
B)  current and electric field 
C)  current density and potential difference 
D)  current density and electric field 
E)  potential difference and electric field

Question 5

Energy may be measured in:

Accepted Answer

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

Question 6

A current of 0.5 ampere exists in a 60-ohm lamp. The applied potential difference is:

Accepted Answer

A)  15 V 
B)  30 V 
C)  60 V 
D)  120 V 
E)  none of these 
A)  15 V 
B)  30 V 
C)  60 V 
D)  120 V 
E)  none of these

Question 7

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 8

You buy a "75 W" light bulb. The label means that:

Accepted Answer

A)  no matter how you use the bulb, the power will be 75 W 
B)  the bulb was filled with 75 W at the factory 
C)  the actual power dissipated will be much higher than 75 W since most of the power appears as heat 
D)  the bulb is expected to "burn out" after you use up its 75 watts 
E)  none of the above 
A)  no matter how you use the bulb, the power will be 75 W 
B)  the bulb was filled with 75 W at the factory 
C)  the actual power dissipated will be much higher than 75 W since most of the power appears as heat 
D)  the bulb is expected to "burn out" after you use up its 75 watts 
E)  none of the above

Question 9

Current has units:

Accepted Answer

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

Question 10

A flat iron is marked "120 volt, 600 watt". In normal use, the current in it is:

Accepted Answer

A)  2 A 
B)  4 A 
C)  5 A 
D)  7.2 A 
E)  0.2 A 
A)  2 A 
B)  4 A 
C)  5 A 
D)  7.2 A 
E)  0.2 A

Question 11

Current is a measure of:

Accepted Answer

A)  force that moves a charge past a point 
B)  resistance to the movement of a charge past a point 
C)  energy used to move a charge past a point 
D)  amount of charge that moves past a point per unit time 
E)  speed with which a charge moves past a point 
A)  force that moves a charge past a point 
B)  resistance to the movement of a charge past a point 
C)  energy used to move a charge past a point 
D)  amount of charge that moves past a point per unit time 
E)  speed with which a charge moves past a point

Question 12

The mechanical equivalent of heat is 1 cal = 4.18 J. A heating coil, connected to a 120-V source, develops 60,000 calories in 10 minutes. The current in the coil is:

Accepted Answer

A)  0.83 A 
B)  2 A 
C)  3.5 A 
D)  20 A 
E)  50 A 
A)  0.83 A 
B)  2 A 
C)  3.5 A 
D)  20 A 
E)  50 A

Question 13

Which of the following graphs best represents the current-voltage relationship of an incandescent light bulb?

Accepted Answer

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

Question 14

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 15

The mechanical equivalent of heat is 1 cal = 4.18 J. The specific heat of water is 1 cal/g·K. An electric immersion water heater, rated at 400 W, should heat a liter of water from 10$\degree$C to 30$\degree$C in about:

Accepted Answer

A)  3.5 min 
B)  1 min 
C)  15 min 
D)  45 min 
E)  15 s 
A)  3.5 min 
B)  1 min 
C)  15 min 
D)  45 min 
E)  15 s

Question 16

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

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

The current is zero in a conductor when no potential difference is applied because:

Accepted Answer

A)  the electrons are not moving 
B)  the electrons are not moving fast enough 
C)  for every electron with a given velocity there is another with a velocity of equal magnitude and opposite direction 
D)  equal numbers of electrons and protons are moving together 
E)  otherwise Ohm's law would not be valid 
A)  the electrons are not moving 
B)  the electrons are not moving fast enough 
C)  for every electron with a given velocity there is another with a velocity of equal magnitude and opposite direction 
D)  equal numbers of electrons and protons are moving together 
E)  otherwise Ohm's law would not be valid

Question 19

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 20

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

Exam 26: Current and Resistance

For a cylindrical resistor made of ohmic material, the resistance does NOT depend on:

An certain resistor dissipates 0.5 W when connected to a 3 V potential difference. When connected to a 1 V potential difference, this resistor will dissipate:

A 60-watt light bulb carries a current of 0.5 ampere. The total charge passing through it in one hour is:

For an ohmic substance the resistivity is the proportionality constant for:

Energy may be measured in:

A current of 0.5 ampere exists in a 60-ohm lamp. The applied potential difference is:

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

You buy a "75 W" light bulb. The label means that:

Current has units:

A flat iron is marked "120 volt, 600 watt". In normal use, the current in it is:

Current is a measure of:

The mechanical equivalent of heat is 1 cal = 4.18 J. A heating coil, connected to a 120-V source, develops 60,000 calories in 10 minutes. The current in the coil is:

Which of the following graphs best represents the current-voltage relationship of an incandescent light bulb?

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

The mechanical equivalent of heat is 1 cal = 4.18 J. The specific heat of water is 1 cal/g·K. An electric immersion water heater, rated at 400 W, should heat a liter of water from 10 °\degree° C to 30 °\degree° C in about:

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?

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:

The current is zero in a conductor when no potential difference is applied because:

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?

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

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The mechanical equivalent of heat is 1 cal = 4.18 J. The specific heat of water is 1 cal/g·K. An electric immersion water heater, rated at 400 W, should heat a liter of water from 10 $\degree$ C to 30 $\degree$ C in about:

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: