Question 1

When the voltage across a resistor is decreased by 50%, what happens to the power dissipated?

Accepted Answer

A)  It increases by 50%. 
B)  It decreases by 50%. 
C)  It decreases by 25%. 
D)  It decreases by 71%. 
E)  It decreases by 75%. 
A)  It increases by 50%. 
B)  It decreases by 50%. 
C)  It decreases by 25%. 
D)  It decreases by 71%. 
E)  It decreases by 75%.

Question 2

Four 12 Ω resistors are connected together. Which of the following resistances cannot be formed using all 4 resistors?

Accepted Answer

A)  48 Ω 
B)  9.0 Ω 
C)  12 Ω 
D)  60 Ω 
E)  20 Ω 
A)  48 Ω 
B)  9.0 Ω 
C)  12 Ω 
D)  60 Ω 
E)  20 Ω

Question 3

Copper has 8.5 × 1028 current-carrying electrons per m3. A copper wire of radius 0.15 mm carries a current of 17 mA. What is the average drift velocity for the electrons?

Accepted Answer

A)  2.7 × 10−9 m/s 
B)  56 × 10−6 m/s 
C)  18 × 10−6 m/s 
D)  more information is needed for this calculation 
A)  2.7 × 10−9 m/s 
B)  56 × 10−6 m/s 
C)  18 × 10−6 m/s 
D)  more information is needed for this calculation

Question 4

Two copper wires, one with twice the diameter of the other, have the same current flowing through them. If the thinner wire has a drift velocity v1, and the thicker wire has a drift velocity v2, how do the drift velocities compare?

Accepted Answer

A)  v1 = v2 
B)  v1 = 2 v2 
C)  2 v1 = v2 
D)  v1 = 4 v2 
E)  4 v1 = v2 
A)  v1 = v2 
B)  v1 = 2 v2 
C)  2 v1 = v2 
D)  v1 = 4 v2 
E)  4 v1 = v2

Question 5

A 2.0 Ω resistor is connected across a 6.0 V power supply. An ammeter with internal resistance of 1.0 Ω is used to measure the current in this circuit. What is the ammeter reading?

Accepted Answer

A)  4.0 A 
B)  3.0 A 
C)  2.0 A 
D)  1.0 A 
E)  an ammeter with less resistance than the rest of the circuit will not produce a reading 
A)  4.0 A 
B)  3.0 A 
C)  2.0 A 
D)  1.0 A 
E)  an ammeter with less resistance than the rest of the circuit will not produce a reading

Question 6

In order to protect a delicate electronic component in a circuit from large currents, a fuse should be placed

Accepted Answer

A)  internally inside the component. 
B)  in contact with the ground and the component. 
C)  in series with the component. 
D)  in parallel with the component. 
A)  internally inside the component. 
B)  in contact with the ground and the component. 
C)  in series with the component. 
D)  in parallel with the component.

Question 7

A length of wire has a resistance of 18.0 Ω. When the wire is uniformly stretched (i.e., the total volume of the wire is unchanged during the stretching) to triple it original length, what resistance results?

Accepted Answer

A)  162 Ω 
B)  54.0 Ω 
C)  18.0 Ω 
D)  6.00 Ω 
E)  2.00 Ω 
A)  162 Ω 
B)  54.0 Ω 
C)  18.0 Ω 
D)  6.00 Ω 
E)  2.00 Ω

Question 8

If 64 coulombs flow along a wire in 4.0 seconds, what is the average current?

Accepted Answer

A)  64 A 
B)  32 A 
C)  16 A 
D)  4.0 A 
E)  none of these choices are correct 
A)  64 A 
B)  32 A 
C)  16 A 
D)  4.0 A 
E)  none of these choices are correct

Question 9

A good ammeter has ________ resistance and a good voltmeter has ________ resistance. "Good" means that it affects the system being measured by very little.

Accepted Answer

A)  low, low 
B)  low, high 
C)  high, high 
D)  high, low 
E)  medium, no 
A)  low, low 
B)  low, high 
C)  high, high 
D)  high, low 
E)  medium, no

Question 10

A series circuit consists of a 12.0 V source of emf, a 2.00 mF capacitor, a 1000 Ω resistor, and a switch. When the switch is closed, how long does it take for the current to reach one-tenth its maximum value?

Accepted Answer

A)  0.693 s 
B)  2.30 s 
C)  4.61 s 
D)  9.00 s 
E)  18.0 s 
A)  0.693 s 
B)  2.30 s 
C)  4.61 s 
D)  9.00 s 
E)  18.0 s

Question 11

Raising the current through a resistor from 8.50 A to 11.3 A increases the power by

Accepted Answer

A)  33%. 
B)  77%. 
C)  113%. 
D)  157%. 
E)  0% (no change). 
A)  33%. 
B)  77%. 
C)  113%. 
D)  157%. 
E)  0% (no change).

Question 12

Three resistors, R1 = 9.0 Ω, R2 = 3.0 Ω, and R3 = 1.0 Ω, are connected in parallel to a 9.0 V battery. What is the power dissipated by R2?

Accepted Answer

A)  2.0 W 
B)  3.0 W 
C)  9.0 W 
D)  27 W 
E)  81 W 
A)  2.0 W 
B)  3.0 W 
C)  9.0 W 
D)  27 W 
E)  81 W

Question 13

In an RC circuit with an initially uncharged capacitor, the time constant is the time that is required for the charge on the capacitor to reach what percentage of its final value?

Accepted Answer

A)  50% 
B)  37% 
C)  100% 
D)  63% 
E)  90% 
A)  50% 
B)  37% 
C)  100% 
D)  63% 
E)  90%

Question 14

Aluminum has a resistivity of 2.65 × 10−8 Ω × m. What is the resistance of 15 m of aluminum wire with cross-sectional area 1.0 mm2?

Accepted Answer

A)  1.6 Ω 
B)  0.40 Ω 
C)  0.13 Ω 
D)  1.3 × 102 Ω 
E)  56 Ω 
A)  1.6 Ω 
B)  0.40 Ω 
C)  0.13 Ω 
D)  1.3 × 102 Ω 
E)  56 Ω

Question 15

In a liquid, a current is set up between points A and B. Positive ions flow from A to B and carry 6.0 coulombs of positive charge per second, while negative ions move from B to A with 2.0 coulombs of negative charge per second. What is the net current from A to B?

Accepted Answer

A)  8.0 A 
B)  −8.0 A 
C)  4.0 A 
D)  −4.0 A 
E)  12 A 
A)  8.0 A 
B)  −8.0 A 
C)  4.0 A 
D)  −4.0 A 
E)  12 A

Exam 18: Electric Current and Circuits

When the voltage across a resistor is decreased by 50%, what happens to the power dissipated?

Four 12 Ω resistors are connected together. Which of the following resistances cannot be formed using all 4 resistors?

Copper has 8.5 × 1028 current-carrying electrons per m3. A copper wire of radius 0.15 mm carries a current of 17 mA. What is the average drift velocity for the electrons?

Two copper wires, one with twice the diameter of the other, have the same current flowing through them. If the thinner wire has a drift velocity v1, and the thicker wire has a drift velocity v2, how do the drift velocities compare?

A 2.0 Ω resistor is connected across a 6.0 V power supply. An ammeter with internal resistance of 1.0 Ω is used to measure the current in this circuit. What is the ammeter reading?

In order to protect a delicate electronic component in a circuit from large currents, a fuse should be placed

A length of wire has a resistance of 18.0 Ω. When the wire is uniformly stretched (i.e., the total volume of the wire is unchanged during the stretching) to triple it original length, what resistance results?

If 64 coulombs flow along a wire in 4.0 seconds, what is the average current?

A good ammeter has ________ resistance and a good voltmeter has ________ resistance. "Good" means that it affects the system being measured by very little.

A series circuit consists of a 12.0 V source of emf, a 2.00 mF capacitor, a 1000 Ω resistor, and a switch. When the switch is closed, how long does it take for the current to reach one-tenth its maximum value?

Raising the current through a resistor from 8.50 A to 11.3 A increases the power by

Three resistors, R1 = 9.0 Ω, R2 = 3.0 Ω, and R3 = 1.0 Ω, are connected in parallel to a 9.0 V battery. What is the power dissipated by R2?

In an RC circuit with an initially uncharged capacitor, the time constant is the time that is required for the charge on the capacitor to reach what percentage of its final value?

Aluminum has a resistivity of 2.65 × 10−8 Ω × m. What is the resistance of 15 m of aluminum wire with cross-sectional area 1.0 mm2?

In a liquid, a current is set up between points A and B. Positive ions flow from A to B and carry 6.0 coulombs of positive charge per second, while negative ions move from B to A with 2.0 coulombs of negative charge per second. What is the net current from A to B?

Introduction

Motion Along a Line

Motion in a Plane

Force and Newtons Laws of Motion

Circular Motion

Conservation of Energy

Linear Momentum

Torque and Angular Momentum

Fluids

Elasticity and Oscillations

Waves

Sound

Temperature and the Ideal Gas

Heat

Thermodynamics

Electric Forces and Fields

Electric Potential

Magnetic Forces and Fields

Electromagnetic Induction

Alternating Current

Electromagnetic Waves

Reflection and Refraction of Light

Optical Instruments

Interference and Diffraction

Relativity

Early Quantum Physics and the Photon

Quantum Physics

Nuclear Physics

Particle Physics

Filters

Copper has 8.5 × 10²⁸ current-carrying electrons per m³. A copper wire of radius 0.15 mm carries a current of 17 mA. What is the average drift velocity for the electrons?

Two copper wires, one with twice the diameter of the other, have the same current flowing through them. If the thinner wire has a drift velocity v₁, and the thicker wire has a drift velocity v₂, how do the drift velocities compare?

A good ammeter has resistance and a good voltmeter has resistance. "Good" means that it affects the system being measured by very little.

Three resistors, R₁ = 9.0 Ω, R₂ = 3.0 Ω, and R₃ = 1.0 Ω, are connected in parallel to a 9.0 V battery. What is the power dissipated by R₂?

Aluminum has a resistivity of 2.65 × 10⁻⁸ Ω × m. What is the resistance of 15 m of aluminum wire with cross-sectional area 1.0 mm²?