Question 1

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?

Accepted Answer

A) 17 C 
B) 15 C 
C) 14 C 
D) 13 C 
E) 60 C 
A) 17 C 
B) 15 C 
C) 14 C 
D) 13 C 
E) 60 C

Question 2

A high-resistance material is used as an insulator between the conductors of a length of coaxial cable.The resistance material,which forms a hollow tube,has an inner radius a and an outer radius b,and the insulator provides a resistance R between the conductors.If a second insulator,made of the same material and having the same length,is made with double both the inner radius and the outer radius of the first,what resistance would it provide between the conductors?

Accepted Answer

A) R 
B) 2 R 
C) 4 R 
D) (ln2)R 
E) R/(ln2) 
A) R 
B) 2 R 
C) 4 R 
D) (ln2)R 
E) R/(ln2)

Question 3

In the Drude model of electrical conduction,the current density is NOT directly proportional to

Accepted Answer

A) the average time interval between successive collisions. 
B) the number of charge carriers per unit volume. 
C) the square of the electron charge. 
D) the electric field present in the wire. 
E) the resistivity of the wire. 
A) the average time interval between successive collisions. 
B) the number of charge carriers per unit volume. 
C) the square of the electron charge. 
D) the electric field present in the wire. 
E) the resistivity of the wire.

Question 4

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. )

Accepted Answer

Question 5

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?

Accepted Answer

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

Question 6

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

Accepted Answer

A) decrease the potential difference between the two ends of the wire. 
B) increase the potential difference between the two ends of the wire. 
C) decrease the magnitude of the electric field in the wire. 
D) heat the wire to a higher temperature. 
E) combine both (b)and (d). 
A) decrease the potential difference between the two ends of the wire. 
B) increase the potential difference between the two ends of the wire. 
C) decrease the magnitude of the electric field in the wire. 
D) heat the wire to a higher temperature. 
E) combine both (b)and (d).

Question 7

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?

Accepted Answer

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

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?

Accepted Answer

A) Arnell,because the resistivity of the wire increases when it is heated. 
B) Arnell,because the resistivity of the wire decreases when it is heated. 
C) Jadeen,because the resistivity of a wire is inversely proportional to its area and directly proportional to its length. 
D) Jadeen,because the resistivity of a copper wire does not decrease when it is hammered. 
E) Both are correct because (a)and (d)are both correct. 
A) Arnell,because the resistivity of the wire increases when it is heated. 
B) Arnell,because the resistivity of the wire decreases when it is heated. 
C) Jadeen,because the resistivity of a wire is inversely proportional to its area and directly proportional to its length. 
D) Jadeen,because the resistivity of a copper wire does not decrease when it is hammered. 
E) Both are correct because (a)and (d)are both correct.

Question 9

A high-voltage transmission line carries 1 000 A at 700 kV for a distance of 100 miles.If the resistance per length in the wire is 0.5 Ω/mile,what is the power loss due to resistive losses?

Accepted Answer

The answer of A high-voltage transmission line carries 1 000...

Question 10

A wire (length = 2.0 m,diameter = 1.0 mm)has a resistance of 0.45Ω.What is the resistivity of the material used to make the wire?

Accepted Answer

A) 5.6 × 10−7 Ω ⋅ m 
B) 1.2 × 10−7 Ω ⋅ m 
C) 1.8 × 10−7 Ω ⋅ m 
D) 2.3 × 10−7 Ω ⋅ m 
E) 7.1 × 10−7 Ω ⋅ m 
A) 5.6 × 10−7 Ω ⋅ m 
B) 1.2 × 10−7 Ω ⋅ m 
C) 1.8 × 10−7 Ω ⋅ m 
D) 2.3 × 10−7 Ω ⋅ m 
E) 7.1 × 10−7 Ω ⋅ m

Question 11

An aluminum wire of cross-sectional area 4.0 mm2 is carrying a current of 8.0 A.The density of aluminum is 2.7 g/cm3,and its molar mass is 27
g.Assuming one free electron per aluminum atom,what is the drift speed of the electrons in this wire?

Accepted Answer

Question 12

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?

Accepted Answer

A)    R 
B)    R 
C) R 
D) 4R 
E) 16R 
A)    R 
B)    R 
C) R 
D) 4R 
E) 16R

Question 13

An electric heater is constructed by applying a potential difference of 110 V across a wire with a resistance of 5.0 Ω.What is the power rating of the heater?

Accepted Answer

A) 2.0 kW 
B) 2.4 kW 
C) 1.7 kW 
D) 1.5 kW 
E) 60 kW 
A) 2.0 kW 
B) 2.4 kW 
C) 1.7 kW 
D) 1.5 kW 
E) 60 kW

Question 14

Most telephone cables are made of copper wire of either 24 or 26 gauge.If the resistance of 24-gauge wire is 137 Ω/mile and the resistance of 26-gauge wire is 220 Ω/mile,what is the ratio of the diameter of 24-gauge wire to that of 26-gauge wire?

Accepted Answer

A) 1.6 
B) 1.3 
C) 0.62 
D) 0.79 
E) 0.88 
A) 1.6 
B) 1.3 
C) 0.62 
D) 0.79 
E) 0.88

Exam 27: Current and Resistance

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?

In the Drude model of electrical conduction,the current density is NOT directly proportional to

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. )

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

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?

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 high-voltage transmission line carries 1 000 A at 700 kV for a distance of 100 miles.If the resistance per length in the wire is 0.5 Ω/mile,what is the power loss due to resistive losses?

A wire (length = 2.0 m,diameter = 1.0 mm)has a resistance of 0.45Ω.What is the resistivity of the material used to make the wire?

An aluminum wire of cross-sectional area 4.0 mm2 is carrying a current of 8.0 A.The density of aluminum is 2.7 g/cm3,and its molar mass is 27 g.Assuming one free electron per aluminum atom,what is the drift speed of the electrons in this wire?

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?

An electric heater is constructed by applying a potential difference of 110 V across a wire with a resistance of 5.0 Ω.What is the power rating of the heater?

Most telephone cables are made of copper wire of either 24 or 26 gauge.If the resistance of 24-gauge wire is 137 Ω/mile and the resistance of 26-gauge wire is 220 Ω/mile,what is the ratio of the diameter of 24-gauge wire to that of 26-gauge wire?

Physics and Measurement

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The Laws of Motion

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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. )

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?

An aluminum wire of cross-sectional area 4.0 mm² is carrying a current of 8.0 A.The density of aluminum is 2.7 g/cm³,and its molar mass is 27 g.Assuming one free electron per aluminum atom,what is the drift speed of the electrons in this wire?