A small bulb is rated at 7.50 W when operated at 125 V. The tungsten filament has a temperature coefficient of resistivity α = 4.50 × 10−3 / °C. When the filament is hot and glowing, its temperature is seven times room temperature (20 °C). What is the resistance of the filament (in ohms) at room temperature?

A) 234 B) 1 350 C) 2 080 D) 4 530 E) 5 630 A) 234 B) 1 350 C) 2 080 D) 4 530 E) 5 630

The electron density in copper is 8.49 × 1028 electrons/m3. The electron charge is e = −1.60 × 10−19 C. When a 1.00 A current is present in a copper wire with a 0.40 cm2 cross-section, the electron drift velocity, in m/s, with direction defined relative to the current density, is

A) −1.84 × 10−6. B) +1.84 × 10−6. C) −1.84. D) −5.43 × 105. E) +5.43 × 105. A) −1.84 × 10−6. B) +1.84 × 10−6. C) −1.84. D) −5.43 × 105. E) +5.43 × 105.

A rod of 2.0-m length and a square (2.0 mm × 2.0 mm) cross section is made of a material with a resistivity of 6.0 × 10−8 Ω ⋅ m. If a potential difference of 0.50 V is placed across the ends of the rod, at what rate is heat generated in the rod?

A) 3.0 W B) 5.3 W C) 8.3 W D) 1.3 W E) 17 W A) 3.0 W B) 5.3 W C) 8.3 W D) 1.3 W E) 17 W

What is the resistance of a wire made of a material with a resistivity of 3.2 × 10−8 Ω ⋅ m if its length is 2.5 m and its diameter is 0.50 mm?

A) 0.16 Ω B) 0.10 Ω C) 1.28 Ω D) 0.41 Ω E) 0.81 Ω A) 0.16 Ω B) 0.10 Ω C) 1.28 Ω D) 0.41 Ω E) 0.81 Ω

Exam 27: Current and Resistance

A copper cable is to be designed to carry a current of 300 A with a power loss of only 2.0 watts per meter. What is the required radius of the copper cable? (The resistivity of copper is 1.7 × 10−⁸ Ω ⋅ m.)

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Question 1

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1.6 cm

If 5.0 × 10²¹ electrons pass through a 20-Ω resistor in 10 min, what is the potential difference across the resistor?

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Question 2

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A 4.0-Ω resistor has a current of 3.0 A in it for 5.0 min. How many electrons pass through the resistor during this time interval?

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Question 3

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What maximum power can be generated from an 18-V emf using any combination of a 6.0-Ω resistor and a 9.0-Ω resistor?

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Question 4

A small bulb is rated at 7.50 W when operated at 125 V. The tungsten filament has a temperature coefficient of resistivity α = 4.50 × 10−³ / °C. When the filament is hot and glowing, its temperature is seven times room temperature (20 °C). What is the resistance of the filament (in ohms) at room temperature?

(Multiple Choice)

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Question 5

A small bulb is rated at 7.5 W when operated at 125 V. Its resistance (in ohms) is

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Question 6

Jadeen says that you can increase the resistance of a copper wire by hammering the wire to make it narrower and longer. Arnell says that you can increase its resistance by heating the wire. Which one, if either, is correct, and why?

(Multiple Choice)

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Question 7

A light bulb is rated at 30 W when operated at 120 V. How much charge enters (and leaves) the light bulb in 1.0 min?

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Question 8

Jadeen says that you can increase the resistance of a copper wire by hammering the wire to make it narrower and longer. Arnell says that you can increase its resistance by heating the wire. Which one, if either, is correct, and why?

(Multiple Choice)

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Question 9

The temperature coefficient of resistivity of iron is 5.0 × 10−³ / °C; that of carbon is −0.50 × 10−³ / °C. When an iron wire and a carbon rod, each having the same 10 Ω resistance at 20°C, are cooled from that temperature to −80°C, the new ratio of the resistance of the carbon rod to the resistance of the iron wire at the lower temperature is

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Question 10

To increase the current density in a wire of length and diameter D, you can

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Question 11

The electron density in copper is 8.49 × 10²⁸ electrons/m³. The electron charge is e = −1.60 × 10−¹⁹ C. When a 1.00 A current is present in a copper wire with a 0.40 cm² cross-section, the electron drift velocity, in m/s, with direction defined relative to the current density, is

(Multiple Choice)

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Question 12

The heating coil of a hot water heater has a resistance of 20 ohms and operates at 210 V. If electrical energy costs 5.5 cents per kW-hr, what does it cost to raise the 200 kg of water in the tank from 15°C to 80°C? (The specific heat of water is 4 186 J/kg°C)

(Short Answer)

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Question 13

Light bulb A is rated at 60 W and light bulb B is rated at 100 W. Both are designed to operate at 110 V. Which statement is correct?

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Question 14

A rod of 2.0-m length and a square (2.0 mm × 2.0 mm) cross section is made of a material with a resistivity of 6.0 × 10−⁸ Ω ⋅ m. If a potential difference of 0.50 V is placed across the ends of the rod, at what rate is heat generated in the rod?

(Multiple Choice)

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Question 15

What is the resistance of 1 000 m of 4-mm diameter copper wire? (ρ_Cu = 1.7 × 10^-8 Ω ⋅ m)

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Question 16

How much energy is dissipated as heat during a two-minute time interval by a 1.5-kΩ resistor which has a constant 20-V potential difference across its leads?

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Question 17

What is the resistance of a wire made of a material with a resistivity of 3.2 × 10−⁸ Ω ⋅ m if its length is 2.5 m and its diameter is 0.50 mm?

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Question 18

A conductor of radius r, length and resistivity ρ has resistance R. What is the new resistance if it is stretched to 4 times its original length?

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Question 19

A conductor of radius r, length and resistivity ρ has resistance R. It is melted down and formed into a new conductor, also cylindrical, with one fourth the length of the original conductor. The resistance of the new conductor is

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Question 20

Showing 1 - 20 of 34

Exam 27: Current and Resistance

A copper cable is to be designed to carry a current of 300 A with a power loss of only 2.0 watts per meter. What is the required radius of the copper cable? (The resistivity of copper is 1.7 × 10−8 Ω ⋅ m.)

If 5.0 × 1021 electrons pass through a 20-Ω resistor in 10 min, what is the potential difference across the resistor?

A 4.0-Ω resistor has a current of 3.0 A in it for 5.0 min. How many electrons pass through the resistor during this time interval?

What maximum power can be generated from an 18-V emf using any combination of a 6.0-Ω resistor and a 9.0-Ω resistor?

A small bulb is rated at 7.5 W when operated at 125 V. Its resistance (in ohms) is

Jadeen says that you can increase the resistance of a copper wire by hammering the wire to make it narrower and longer. Arnell says that you can increase its resistance by heating the wire. Which one, if either, is correct, and why?

A light bulb is rated at 30 W when operated at 120 V. How much charge enters (and leaves) the light bulb in 1.0 min?

Jadeen says that you can increase the resistance of a copper wire by hammering the wire to make it narrower and longer. Arnell says that you can increase its resistance by heating the wire. Which one, if either, is correct, and why?

To increase the current density in a wire of length and diameter D, you can

The electron density in copper is 8.49 × 1028 electrons/m3. The electron charge is e = −1.60 × 10−19 C. When a 1.00 A current is present in a copper wire with a 0.40 cm2 cross-section, the electron drift velocity, in m/s, with direction defined relative to the current density, is

The heating coil of a hot water heater has a resistance of 20 ohms and operates at 210 V. If electrical energy costs 5.5 cents per kW-hr, what does it cost to raise the 200 kg of water in the tank from 15°C to 80°C? (The specific heat of water is 4 186 J/kg°C)

Light bulb A is rated at 60 W and light bulb B is rated at 100 W. Both are designed to operate at 110 V. Which statement is correct?

A rod of 2.0-m length and a square (2.0 mm × 2.0 mm) cross section is made of a material with a resistivity of 6.0 × 10−8 Ω ⋅ m. If a potential difference of 0.50 V is placed across the ends of the rod, at what rate is heat generated in the rod?

What is the resistance of 1 000 m of 4-mm diameter copper wire? (ρCu = 1.7 × 10-8 Ω ⋅ m)

How much energy is dissipated as heat during a two-minute time interval by a 1.5-kΩ resistor which has a constant 20-V potential difference across its leads?

What is the resistance of a wire made of a material with a resistivity of 3.2 × 10−8 Ω ⋅ m if its length is 2.5 m and its diameter is 0.50 mm?

A conductor of radius r, length and resistivity ρ has resistance R. What is the new resistance if it is stretched to 4 times its original length?

A conductor of radius r, length and resistivity ρ has resistance R. It is melted down and formed into a new conductor, also cylindrical, with one fourth the length of the original conductor. The resistance of the new conductor is

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A copper cable is to be designed to carry a current of 300 A with a power loss of only 2.0 watts per meter. What is the required radius of the copper cable? (The resistivity of copper is 1.7 × 10−⁸ Ω ⋅ m.)

If 5.0 × 10²¹ electrons pass through a 20-Ω resistor in 10 min, what is the potential difference across the resistor?

The electron density in copper is 8.49 × 10²⁸ electrons/m³. The electron charge is e = −1.60 × 10−¹⁹ C. When a 1.00 A current is present in a copper wire with a 0.40 cm² cross-section, the electron drift velocity, in m/s, with direction defined relative to the current density, is

A rod of 2.0-m length and a square (2.0 mm × 2.0 mm) cross section is made of a material with a resistivity of 6.0 × 10−⁸ Ω ⋅ m. If a potential difference of 0.50 V is placed across the ends of the rod, at what rate is heat generated in the rod?

What is the resistance of 1 000 m of 4-mm diameter copper wire? (ρ_Cu = 1.7 × 10^-8 Ω ⋅ m)

What is the resistance of a wire made of a material with a resistivity of 3.2 × 10−⁸ Ω ⋅ m if its length is 2.5 m and its diameter is 0.50 mm?