Question 1

If a lamp has resistance of 120 W when it operates at 100 W, what is the applied voltage?

Accepted Answer

A)  110 V
B)  120 V
C)  125 V
D)  220 V

Question 2

A light bulb with a tungsten filament is attached to a source of variable voltage. As the voltage is increased on the bulb,

Accepted Answer

A)  the bulb's resistance decreases.
B)  the bulb's resistance increases.
C)  the current in the bulb decreases.
D)  the power dissipated remains constant.

Question 3

A copper cable needs to carry a current of 200 A with a power loss of only 3.0 W/m.What is the required radius of the copper cable? (The resistivity of copper is 1.7 * 10-8 W*m) .

Accepted Answer

A)  0.21 cm
B)  0.85 cm
C)  3.2 cm
D)  4.0 cm

Question 4

You measure a 25.0-V potential difference across a 5.00-W resistor.What is the current flowing through it?

Accepted Answer

A)  125 A
B)  5.00 A
C)  4.00 A
D)  1.00 A

Question 5

Two cylindrical resistors are made of the same material and have the same resistance.The resistors, R1 and R2, have different radii, r1 and r2, and different lengths, L1 and L2.Which of the following relative values for radii and lengths would result in equal resistances?

Accepted Answer

A)  r1 = r2 and L1 = 2L2
B)  2r1 = r2 and L1 = 2L2
C)  r1 = r2 and 4L1 = L2
D)  2r1 = r2 and 4L1 = L2

Question 6

When a superconductor's temperature drops below the critical temperature, its resistance:

Accepted Answer

A)  equals that of a semiconductor of equal dimensions.
B)  increases by two.
C)  drops to zero.
D)  reduces to one half.

Question 7

A wire carries a steady current of 0.1 A over a period of 20 s.What total charge passes through the wire in this time interval?

Accepted Answer

A)  200 C
B)  20 C
C)  2 C
D)  0.005 C

Question 8

A high-voltage transmission line carries 1 000 A at 700 kV for a distance of 100 miles.If the resistance in the wire is 1 W/mile, what is the power loss due to resistive losses?

Accepted Answer

A)  10 kW
B)  100 kW
C)  10 MW
D)  100 MW

Question 9

Suppose that a voltage surge produces 140 V for a moment in a 120-V line.What will temporarily be the output of a 100-W light bulb assuming its resistance does not change?

Accepted Answer

A)  109 W
B)  118 W
C)  127 W
D)  136 W

Question 10

When the voltage across a nonohmic resistor is doubled, the current through it triples.What happens to the power delivered to this resistor?

Accepted Answer

A)  This cannot be answered with the information given.
B)  The power decreases to 2/3 of the original amount.
C)  The power increases to 1.5 times the original amount.
D)  The power increases to 6 times the original amount.

Question 11

If a metallic wire of cross sectional area 3.0 * 10-6 m2 carries a current of 6.0 A and has a mobile charge density of 4.24 * 1028 carriers/m3, what is the average drift velocity of the mobile charge carriers? (charge value = 1.6 * 10-19 C)

Accepted Answer

A)  3.4 * 103 m/s
B)  1.7 * 103 m/s
C)  1.5 * 10-4 m/s
D)  2.9 * 10-4 m/s

Question 12

A light bulb has resistance of 240 W when operating at 120 V.Find the current in the light bulb.

Accepted Answer

A)  2.0 A
B)  1.0 A
C)  0.50 A
D)  0.20 A

Question 13

Which process will double the power given off by a resistor?

Accepted Answer

A)  doubling the current while doubling the resistance
B)  doubling the current by making a resistance half as big
C)  doubling the current by doubling the voltage
D)  doubling the current while making the voltage half as big

Question 14

A resistor is made of a material that has a resistivity that is proportional to the current going through it. If the voltage across the resistor is doubled, what happens to the power dissipated by it?

Accepted Answer

A)  It doubles.
B)  It quadruples.
C)  It increases by a factor of 23/2.
D)  It increases by a factor of 21/2.

Question 15

A metal wire has a resistance of 25.00 W under room temperature conditions of 25 °\degree° C.When the wire is heated to 85 °\degree° C the resistance increases by 0.75 W.What is the temperature coefficient of resistivity of this metal?

Accepted Answer

A)  5.0 * 10-4 ( °\degree° 
C)  -1
B)  1.3 * 10-3 ( °\degree° 
C)  -1
C)  1.5 * 10-3 ( °\degree° 
C)  -1
D)  2.5 * 10-3 ( °\degree° 
C)  -1

Question 16

An electric clothes dryer draws 15 A at 220 V.If the clothes put into the dryer have a mass of 7.0 kg when wet and 4.0 kg dry, how long does it take to dry the clothes? (Assume all heat energy goes into vaporizing water, Lv = 2.26 * 106 J/kg) .

Accepted Answer

A)  55 min
B)  34 min
C)  20 min
D)  16 min

Question 17

A wire has resistance R.A second wire has twice the length, twice the diameter, and twice the resistivity of the first wire.What is its resistance?

Accepted Answer

A)  8 R
B)  R
C)  R/4
D)  The resistance is not given.

Question 18

A metallic conductor has a resistivity of 18 * 10-6 W*m.What is the resistance of a piece that is 30 m long and has a uniform cross sectional area of 3.0 * 10-6 m2?

Accepted Answer

A)  0.056 W
B)  180 W
C)  160 W
D)  90 W

Question 19

The temperature coefficient of resistivity is a quantity that is:

Accepted Answer

A)  always positive.
B)  always non-negative.
C)  sometimes negative.
D)  represented by the symbol s.

Question 20

A metal wire has a resistance of 10.00 W at a temperature of 20 °\degree° C.If the same wire has a resistance of 10.55 W at 90 °\degree° C, what is the resistance when its temperature is -20 °\degree° C?

Accepted Answer

A)  0.70 W
B)  9.69 W
C)  10.31 W
D)  13.8 W

Exam 17: Current and Resistance

A copper cable needs to carry a current of 200 A with a power loss of only 3.0 W/m.What is the required radius of the copper cable? (The resistivity of copper is 1.7 * 10-8 W*m) .

Correct AnswerverifiedShow Answer

A metal wire has a resistance of 10.00 W at a temperature of 20 °\degree° C.If the same wire has a resistance of 10.55 W at 90 °\degree° C, what is the resistance when its temperature is -20 °\degree° C?

Correct AnswerverifiedShow Answer

A resistor is made of a material that has a resistivity that is proportional to the current going through it. If the voltage across the resistor is doubled, what happens to the power dissipated by it?

Correct AnswerverifiedShow Answer

Which process will double the power given off by a resistor?

Correct AnswerverifiedShow Answer

A wire has resistance R.A second wire has twice the length, twice the diameter, and twice the resistivity of the first wire.What is its resistance?

Correct AnswerverifiedShow Answer

Suppose that a voltage surge produces 140 V for a moment in a 120-V line.What will temporarily be the output of a 100-W light bulb assuming its resistance does not change?

Correct AnswerverifiedShow Answer

When a superconductor's temperature drops below the critical temperature, its resistance:

Correct AnswerverifiedShow Answer

If a lamp has resistance of 120 W when it operates at 100 W, what is the applied voltage?

Correct AnswerverifiedShow Answer

A wire carries a steady current of 0.1 A over a period of 20 s.What total charge passes through the wire in this time interval?

Correct AnswerverifiedShow Answer

An electric clothes dryer draws 15 A at 220 V.If the clothes put into the dryer have a mass of 7.0 kg when wet and 4.0 kg dry, how long does it take to dry the clothes? (Assume all heat energy goes into vaporizing water, Lv = 2.26 * 106 J/kg) .

Correct AnswerverifiedShow Answer

Two cylindrical resistors are made of the same material and have the same resistance.The resistors, R1 and R2, have different radii, r1 and r2, and different lengths, L1 and L2.Which of the following relative values for radii and lengths would result in equal resistances?

Correct AnswerverifiedShow Answer

If a metallic wire of cross sectional area 3.0 * 10-6 m2 carries a current of 6.0 A and has a mobile charge density of 4.24 * 1028 carriers/m3, what is the average drift velocity of the mobile charge carriers? (charge value = 1.6 * 10-19 C)

Correct AnswerverifiedShow Answer

You measure a 25.0-V potential difference across a 5.00-W resistor.What is the current flowing through it?

Correct AnswerverifiedShow Answer

A light bulb with a tungsten filament is attached to a source of variable voltage. As the voltage is increased on the bulb,

Correct AnswerverifiedShow Answer

A high-voltage transmission line carries 1 000 A at 700 kV for a distance of 100 miles.If the resistance in the wire is 1 W/mile, what is the power loss due to resistive losses?

Correct AnswerverifiedShow Answer

A metal wire has a resistance of 25.00 W under room temperature conditions of 25 °\degree° C.When the wire is heated to 85 °\degree° C the resistance increases by 0.75 W.What is the temperature coefficient of resistivity of this metal?

Correct AnswerverifiedShow Answer

When the voltage across a nonohmic resistor is doubled, the current through it triples.What happens to the power delivered to this resistor?

Correct AnswerverifiedShow Answer

The temperature coefficient of resistivity is a quantity that is:

Correct AnswerverifiedShow Answer

A light bulb has resistance of 240 W when operating at 120 V.Find the current in the light bulb.

Correct AnswerverifiedShow Answer

A metallic conductor has a resistivity of 18 * 10-6 W*m.What is the resistance of a piece that is 30 m long and has a uniform cross sectional area of 3.0 * 10-6 m2?

Correct AnswerverifiedShow Answer

A copper cable needs to carry a current of 200 A with a power loss of only 3.0 W/m.What is the required radius of the copper cable? (The resistivity of copper is 1.7 * 10^-8 W*m) .

Correct Answer
verified

A metal wire has a resistance of 10.00 W at a temperature of 20 $\degree$ C.If the same wire has a resistance of 10.55 W at 90 $\degree$ C, what is the resistance when its temperature is -20 $\degree$ C?

Correct Answer
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Correct Answer
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Correct Answer
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An electric clothes dryer draws 15 A at 220 V.If the clothes put into the dryer have a mass of 7.0 kg when wet and 4.0 kg dry, how long does it take to dry the clothes? (Assume all heat energy goes into vaporizing water, L_v = 2.26 * 10⁶ J/kg) .

Correct Answer
verified

Two cylindrical resistors are made of the same material and have the same resistance.The resistors, R₁ and R₂, have different radii, r₁ and r₂, and different lengths, L₁ and L₂.Which of the following relative values for radii and lengths would result in equal resistances?

Correct Answer
verified

If a metallic wire of cross sectional area 3.0 * 10^-6 m² carries a current of 6.0 A and has a mobile charge density of 4.24 * 10²⁸ carriers/m³, what is the average drift velocity of the mobile charge carriers? (charge value = 1.6 * 10^-19 C)

Correct Answer
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Correct Answer
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Correct Answer
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A metal wire has a resistance of 25.00 W under room temperature conditions of 25 $\degree$ C.When the wire is heated to 85 $\degree$ C the resistance increases by 0.75 W.What is the temperature coefficient of resistivity of this metal?

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
verified

A metallic conductor has a resistivity of 18 * 10^-6 Wm.What is the resistance of a piece that is 30 m long and has a uniform cross sectional area of 3.0 10^-6 m²?

Correct Answer
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