Question 1

A 20-W platinum wire at 20$\degree$C with a temperature coefficient of resistivity of 3.9 * 10-3 ($\degree$C)-1 will have what resistance at 100$\degree$C?

Accepted Answer

A) 14 W 
B) 20 W 
C) 26 W 
D) 28 W 
A) 14 W 
B) 20 W 
C) 26 W 
D) 28 W C

Question 2

A wire 1 mm in diameter is connected to one end of a wire of the same material 2 mm in diameter of twice the length.A voltage source is connected to the wires and a current is passed through the wires.If it takes time T for the average conduction electron to traverse the 1-mm wire, how long does it take for such an electron to traverse the 2-mm wire?

Accepted Answer

A) T/4 
B) T 
C) 4T 
D) 8T 
A) T/4 
B) T 
C) 4T 
D) 8T D

Question 3

The resistivity of a material is doubled when heated a certain amount.What happens to the resistance of a resistor made of this material when heated the same amount?

Accepted Answer

A) It doubles. 
B) It quadruples. 
C) It halves. 
D) It stays the same. 
A) It doubles. 
B) It quadruples. 
C) It halves. 
D) It stays the same. A

Question 4

Which is a unit of power?

Accepted Answer

A) kWh 
B) W/s 
C) A*W 
D) J/s 
A) kWh 
B) W/s 
C) A*W 
D) J/s

Question 5

The size of the electric current in a electrical conductor is a function of which of the following?

Accepted Answer

A) velocity of charge carriers 
B) conductor cross sectional area 
C) density of charge carriers 
D) All of the above choices are valid. 
A) velocity of charge carriers 
B) conductor cross sectional area 
C) density of charge carriers 
D) All of the above choices are valid.

Question 6

Wire A and Wire B are each carrying the same current.If the diameter of Wire A is twice that of Wire B, how does the drift velocity vdA in Wire A compare to that in in Wire B?

Accepted Answer

A) vdA = vdB 
B) vdA = 2 vdB 
C) vdA = vdB /2 
D) vdA = vdB /4 
A) vdA = vdB 
B) vdA = 2 vdB 
C) vdA = vdB /2 
D) vdA = vdB /4

Question 7

The current in an electron beam in a cathode-ray tube is measured to be 70 µA.How many electrons hit the screen in 5.0 s? (e = 1.6 * 10-19 C)

Accepted Answer

A) 2.2 * 1011 electrons 
B) 8.8 * 1013 electrons 
C) 2.2 * 1015 electrons 
D) 8.8 * 1018 electrons 
A) 2.2 * 1011 electrons 
B) 8.8 * 1013 electrons 
C) 2.2 * 1015 electrons 
D) 8.8 * 1018 electrons

Question 8

Number 10 copper wire (radius = 1.3 mm) is commonly used for electrical installations in homes.What is the voltage drop in 40 m of #10 copper wire if it carries a current of 10 A? (The resistivity of copper is 1.7 * 10-8 W*m.)

Accepted Answer

A) 1.3 V 
B) 0.77 V 
C) 0.50 V 
D) 0.13 V 
A) 1.3 V 
B) 0.77 V 
C) 0.50 V 
D) 0.13 V

Question 9

Two wires with the same resistance have the same diameter but different lengths.If wire 1 has length L1 and wire 2 has length L2, how do L1 and L2 compare if wire 1 is made from copper and wire 2 is made from aluminum? The resistivity of copper is 1.7 * 10-5 W·m and the resistivity of aluminum is 2.82 * 10-5 W·m.

Accepted Answer

A) L1 = 1.7 L2 
B) L1 = 0.60 L2 
C) L1 = 2.8 L2 
D) L1 = 0.36 L2 
A) L1 = 1.7 L2 
B) L1 = 0.60 L2 
C) L1 = 2.8 L2 
D) L1 = 0.36 L2

Question 10

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 current through 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. 
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 11

Superconductivity was discovered by:

Accepted Answer

A) Volta. 
B) Ohm. 
C) Onnes. 
D) Bednorz and Müller. 
A) Volta. 
B) Ohm. 
C) Onnes. 
D) Bednorz and Müller.

Question 12

If a 500-W heater carries a current of 4.00 A, what is the voltage across the ends of the heating element?

Accepted Answer

A) 2 000 V 
B) 125 V 
C) 250 V 
D) 0.008 V 
A) 2 000 V 
B) 125 V 
C) 250 V 
D) 0.008 V

Question 13

A water pump draws about 3.8 A when connected to 240 V.What is the cost (with electrical energy at 9 cents per kWh) of running the pump for 10 h?

Accepted Answer

A) 8.0 cents 
B) 15 cents 
C) 82 cents 
D) 95 cents 
A) 8.0 cents 
B) 15 cents 
C) 82 cents 
D) 95 cents

Question 14

A high-voltage transmission line carries 1 000 A at 700 000 V.What is the power carried by the line?

Accepted Answer

A) 700 MW 
B) 370 MW 
C) 100 MW 
D) 70 MW 
A) 700 MW 
B) 370 MW 
C) 100 MW 
D) 70 MW

Question 15

The quantity volt is equivalent to which of the following?

Accepted Answer

A) J*m 
B) J*C 
C) C/W 
D) J/C 
A) J*m 
B) J*C 
C) C/W 
D) J/C

Question 16

A steam turbine at an electric power plant delivers 4 500 kW of power to an electrical generator which converts 95% of this mechanical energy into electrical energy.What is the current delivered by the generator if it delivers at 3 600 V?

Accepted Answer

A) 0.66 * 103 A 
B) 1.0 * 103 A 
C) 1.2 * 103 A 
D) 5.9 * 103 A 
A) 0.66 * 103 A 
B) 1.0 * 103 A 
C) 1.2 * 103 A 
D) 5.9 * 103 A

Question 17

When you flip a switch to turn on a light, the delay before the light turns on is determined by:

Accepted Answer

A) the number of electron collisions per second in the wire. 
B) the drift speed of the electrons in the wire. 
C) the speed of the electric field moving in the wire. 
D) none of these, since the light comes on instantly. 
A) the number of electron collisions per second in the wire. 
B) the drift speed of the electrons in the wire. 
C) the speed of the electric field moving in the wire. 
D) none of these, since the light comes on instantly.

Question 18

Some superconductors are capable of carrying a very large quantity of current.If the measured current is 1.00 * 105 A, how many electrons are moving through the superconductor per second? (e = 1.60 * 10-19 C)

Accepted Answer

A) 6.25 * 1023 
B) 3.12 * 1022 
C) 6.25 * 1021 
D) 3.12 * 1020 
A) 6.25 * 1023 
B) 3.12 * 1022 
C) 6.25 * 1021 
D) 3.12 * 1020

Question 19

Materials having resistance changes as voltage or current varies are called:

Accepted Answer

A) ohmic. 
B) inohmic. 
C) nonohmic. 
D) deohmic. 
A) ohmic. 
B) inohmic. 
C) nonohmic. 
D) deohmic.

Question 20

A solar panel measures 80 cm * 50 cm.In direct sunlight, the panel delivers 3.2 A at 15 V.If the intensity of sunlight is 1 000 W/m2, what is the efficiency of the solar panel in converting solar energy into electrical energy?

Accepted Answer

A) 24% 
B) 18% 
C) 12% 
D) 6.0% 
A) 24% 
B) 18% 
C) 12% 
D) 6.0%

Exam 17: Current and Resistance

A 20-W platinum wire at 20 °\degree° C with a temperature coefficient of resistivity of 3.9 * 10-3 ( °\degree° C)-1 will have what resistance at 100 °\degree° C?

The resistivity of a material is doubled when heated a certain amount.What happens to the resistance of a resistor made of this material when heated the same amount?

Which is a unit of power?

The size of the electric current in a electrical conductor is a function of which of the following?

Wire A and Wire B are each carrying the same current.If the diameter of Wire A is twice that of Wire B, how does the drift velocity vdA in Wire A compare to that in in Wire B?

The current in an electron beam in a cathode-ray tube is measured to be 70 µA.How many electrons hit the screen in 5.0 s? (e = 1.6 * 10-19 C)

Number 10 copper wire (radius = 1.3 mm) is commonly used for electrical installations in homes.What is the voltage drop in 40 m of #10 copper wire if it carries a current of 10 A? (The resistivity of copper is 1.7 * 10-8 W*m.)

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 current through it?

Superconductivity was discovered by:

If a 500-W heater carries a current of 4.00 A, what is the voltage across the ends of the heating element?

A water pump draws about 3.8 A when connected to 240 V.What is the cost (with electrical energy at 9 cents per kWh) of running the pump for 10 h?

A high-voltage transmission line carries 1 000 A at 700 000 V.What is the power carried by the line?

The quantity volt is equivalent to which of the following?

A steam turbine at an electric power plant delivers 4 500 kW of power to an electrical generator which converts 95% of this mechanical energy into electrical energy.What is the current delivered by the generator if it delivers at 3 600 V?

When you flip a switch to turn on a light, the delay before the light turns on is determined by:

Some superconductors are capable of carrying a very large quantity of current.If the measured current is 1.00 * 105 A, how many electrons are moving through the superconductor per second? (e = 1.60 * 10-19 C)

Materials having resistance changes as voltage or current varies are called:

A solar panel measures 80 cm * 50 cm.In direct sunlight, the panel delivers 3.2 A at 15 V.If the intensity of sunlight is 1 000 W/m2, what is the efficiency of the solar panel in converting solar energy into electrical energy?

Introduction

Motion in One Dimension

Vectors and Two-Dimensional Motion

The Laws of Motion

Energy

Momentum and Collisions

Rotational Motion and the Law of Gravity

Rotational Equilibrium and Rotational Dynamics

Solids and Fluids

Thermal Physics

Energy in Thermal Processes

The Laws of Thermodynamics

Vibrations and Waves

Sound

Electric Forces and Electric Fields

Electrical Energy and Capacitance

Direct-Current Circuits

Magnetism

Induced Voltages and Inductance

Alternating Current Circuits and Electromagnetic Waves

Reflection and Refraction of Light

Mirrors and Lenses

Wave Optics

Optical Instruments

Relativity

Quantum Physics

Atomic Physics

Nuclear Physics

Nuclear Energy and Elementary Particles

Filters

A 20-W platinum wire at 20 $\degree$ C with a temperature coefficient of resistivity of 3.9 * 10^-3 ( $\degree$ C)^-1 will have what resistance at 100 $\degree$ C?

Wire A and Wire B are each carrying the same current.If the diameter of Wire A is twice that of Wire B, how does the drift velocity v_dA in Wire A compare to that in in Wire B?

The current in an electron beam in a cathode-ray tube is measured to be 70 µA.How many electrons hit the screen in 5.0 s? (e = 1.6 * 10^-19 C)

Number 10 copper wire (radius = 1.3 mm) is commonly used for electrical installations in homes.What is the voltage drop in 40 m of #10 copper wire if it carries a current of 10 A? (The resistivity of copper is 1.7 * 10^-8 W*m.)

Some superconductors are capable of carrying a very large quantity of current.If the measured current is 1.00 * 10⁵A, how many electrons are moving through the superconductor per second? (e = 1.60 * 10^-19 C)

A solar panel measures 80 cm * 50 cm.In direct sunlight, the panel delivers 3.2 A at 15 V.If the intensity of sunlight is 1 000 W/m², what is the efficiency of the solar panel in converting solar energy into electrical energy?