Question 1

A transformer is a device used to

Accepted Answer

A) transform an alternating current into a direct current. 
B) transform a direct current into an alternating current. 
C) increase or decrease an ac voltage. 
D) increase or decrease a dc voltage. 
A) transform an alternating current into a direct current. 
B) transform a direct current into an alternating current. 
C) increase or decrease an ac voltage. 
D) increase or decrease a dc voltage. C

Question 2

A resistor and an inductor are connected in series to an ideal battery of constant terminal voltage.At the moment contact is made with the battery,the voltage across the resistor is

Accepted Answer

A) greater than the battery's terminal voltage. 
B) equal to the battery's terminal voltage. 
C) less than the battery's terminal voltage,but not zero. 
D) zero. 
E) equal to the voltage across the inductor. 
A) greater than the battery's terminal voltage. 
B) equal to the battery's terminal voltage. 
C) less than the battery's terminal voltage,but not zero. 
D) zero. 
E) equal to the voltage across the inductor. D

Question 3

As shown in the figure,a straight wire carries a steady current I.A metal bar is in contact with a pair of rails and is in upward motion with velocity of magnitude ν.The polarity of the induced emf in terminals X and Y is

Accepted Answer

A) X and Y are at the same potential. 
B) X is positive and Y is negative. 
C) Y is positive and X is negative. 
A) X and Y are at the same potential. 
B) X is positive and Y is negative. 
C) Y is positive and X is negative. C

Question 4

As shown in the figure,a metal bar is in contact with a pair of parallel rails.A steady,uniform,magnetic field B is present directed to the right.The bar is moving upward with velocity of magnitude ν.What is the polarity of the induced emf in terminals X and Y?

Accepted Answer

A) X and Y are at the same potential. 
B) X is positive and Y is negative. 
C) Y is positive and X is negative. 
A) X and Y are at the same potential. 
B) X is positive and Y is negative. 
C) Y is positive and X is negative.

Question 5

A flat coil is in a uniform magnetic field.The magnetic flux through the coil is greatest when the plane of its area is

Accepted Answer

A) parallel to the magnetic field. 
B) at 45° with the magnetic field. 
C) perpendicular to the magnetic field. 
A) parallel to the magnetic field. 
B) at 45° with the magnetic field. 
C) perpendicular to the magnetic field.

Question 6

An outer metal ring surrounds an inner metal ring,as shown in the figure.The current in the outer ring is counterclockwise and decreasing.What is the direction of the induced current in the inner ring?

Accepted Answer

A) clockwise 
B) counterclockwise 
C) There is no induced current in the inner ring. 
A) clockwise 
B) counterclockwise 
C) There is no induced current in the inner ring.

Question 7

An ideal step-up transformer doubles a primary voltage of 110 V.What is the ratio of the number of turns in its primary coil to the number of turns in the secondary coil?

Accepted Answer

A) 1:4 
B) 4:1 
C) 2:1 
D) 1:2 
E) 1:8 
A) 1:4 
B) 4:1 
C) 2:1 
D) 1:2 
E) 1:8

Question 8

A transformer is a device that normally

Accepted Answer

A) operates on either dc or ac. 
B) operates only on ac. 
C) operates only on dc. 
A) operates on either dc or ac. 
B) operates only on ac. 
C) operates only on dc.

Question 9

A round flat metal coil has 180 turns and negligible resistance.It is connected in a series circuit with a  
Resistor,with nothing else in the circuit.You measure that a  
Current flows through the resistor when a magnetic field through the coil,perpendicular to its area,is changing at  
What is the radius of the coil?

Accepted Answer

A) 0.25 m 
B) 0.014 m 
C) 0.54 m 
D) 0.043 m 
A) 0.25 m 
B) 0.014 m 
C) 0.54 m 
D) 0.043 m

Question 10

The area of a rectangular loop of wire is 3.6 ×  
 
.The loop is placed in a uniform magnetic field that changes steadily from 0.20 T to 1.4 T in 1.6 s.The plane of the loop is perpendicular to the direction of the magnetic field.What is the magnitude of the induced emf in that loop?

Accepted Answer

A) 2.8 ×   V 
B) 2.7 ×   V 
C) 0 V 
D) 1.8 ×   V 
E) 3.0 ×   V 
A) 2.8 ×   V 
B) 2.7 ×   V 
C) 0 V 
D) 1.8 ×   V 
E) 3.0 ×   V

Question 11

A circular coil lies flat on a horizontal surface.A bar magnet is held above the center of the coil with its north pole pointing down.If the magnet is dropped from this position what is the direction of the induced current in the coil,as viewed from above?

Accepted Answer

A) counterclockwise 
B) clockwise 
C) An emf but no current is induced in the coil. 
D) There is no current in the coil. 
A) counterclockwise 
B) clockwise 
C) An emf but no current is induced in the coil. 
D) There is no current in the coil.

Question 12

The primary coil of an ideal transformer has 100 turns and its secondary coil has 400 turns.If the ac current in the secondary coil is 2 A,what is the current in its primary coil?

Accepted Answer

A) 2 A 
B) 8 A 
C) 1/2 A 
D) 1/4 A 
E) 4 A 
A) 2 A 
B) 8 A 
C) 1/2 A 
D) 1/4 A 
E) 4 A

Question 13

A resistor and an inductor are connected in series to an ideal battery of constant terminal voltage.At the moment contact is made with the battery,the voltage across the inductor is

Accepted Answer

A) greater than the battery's terminal voltage. 
B) equal to the battery's terminal voltage. 
C) less than the battery's terminal voltage,but not zero. 
D) zero. 
E) equal to the voltage across the resistor. 
A) greater than the battery's terminal voltage. 
B) equal to the battery's terminal voltage. 
C) less than the battery's terminal voltage,but not zero. 
D) zero. 
E) equal to the voltage across the resistor.

Question 14

The primary coil of an ideal transformer has 600 turns and its secondary coil has 150 turns.If the current in the primary coil is 2 A,what is the current in its secondary coil?

Accepted Answer

A) 8 A 
B) 1/2 A 
C) 1/4 A 
D) 2 A 
E) 4 A 
A) 8 A 
B) 1/2 A 
C) 1/4 A 
D) 2 A 
E) 4 A

Question 15

In the figure,a bar magnet moves away from the solenoid.The direction of the induced current through the resistor R is

Accepted Answer

A) from a to b. 
B) from b to a. 
C) No current is induced. 
A) from a to b. 
B) from b to a. 
C) No current is induced.

Question 16

A single-turn loop of wire,having a resistance of 8.00 Ω and a cross-sectional area 200 cm2,is perpendicular to a uniform magnetic field that increases steadily from 0.200 T to 2.800 T in 2.20 seconds.What is the magnitude of the induced current in the loop?

Accepted Answer

A) 2.95 A 
B) 3.18 A 
C) 0 A 
D) 3.18 mA 
E) 2.95 mA 
A) 2.95 A 
B) 3.18 A 
C) 0 A 
D) 3.18 mA 
E) 2.95 mA

Question 17

A long vertical wire carries a steady 70 A current.As shown in the figure,a pair of horizontal rails are 0.20 m apart.A 20-Ω resistor connects points a and b,at the end of the rails.A bar is in contact with the rails,and is moved by an external force with a constant horizontal velocity of 0.90 m/s to the right,as shown.The bar and the rails have negligible resistance.At the instant that the bar is 0.20 m from the wire,what are the induced current in the resistor and its direction through the resistor? (μ0 = 4π × 10-7 T ∙ m/A)

Accepted Answer

A) 0.63 μA,from a to b 
B) 0.63 μA,from b to a 
C) 0.32 μA,from a to b 
D) 0.32 μA,from b to a 
E) 1.9 μA,from b to a 
A) 0.63 μA,from a to b 
B) 0.63 μA,from b to a 
C) 0.32 μA,from a to b 
D) 0.32 μA,from b to a 
E) 1.9 μA,from b to a

Question 18

What is the self-inductance of an ideal solenoid that is 300 cm long with a cross-sectional area of 1.00 × 10-4 m2 and has 1000 turns of wire? (μ0 = 4π × 10-7 T ∙ m/A)

Accepted Answer

A) 4.19 nH 
B) 4.19 pH 
C) 4.19 μH 
D) 41.9 nH 
E) 41.9 µH 
A) 4.19 nH 
B) 4.19 pH 
C) 4.19 μH 
D) 41.9 nH 
E) 41.9 µH

Question 19

In an ideal transformer,how many turns are necessary in a 110-V primary if the 24-V secondary has 100 turns?

Accepted Answer

A) 458 
B) 240 
C) 110 
D) 22 
A) 458 
B) 240 
C) 110 
D) 22

Question 20

A conducting rod with a length ℓ = 25 cm is placed on a U-shaped metal wire that is connected to a lightbulb having a resistance of 8.0 Ω as shown in the figure.The wire and the rod are in the plane of the page.A constant uniform magnetic field of strength 0.40 T is applied perpendicular to and into the paper.An external applied force moves the rod to the right with a constant speed of 6.0 m/s.What are the magnitude and direction of the induced current in the circuit?

Accepted Answer

A) 17 mA clockwise 
B) 17 mA counterclockwise 
C) 75 mA counterclockwise 
D) 75 mA clockwise 
E) 52 mA clockwise 
A) 17 mA clockwise 
B) 17 mA counterclockwise 
C) 75 mA counterclockwise 
D) 75 mA clockwise 
E) 52 mA clockwise

Exam 23: Magnetic Flux and Faradays Law of Induction

A transformer is a device used to

A resistor and an inductor are connected in series to an ideal battery of constant terminal voltage.At the moment contact is made with the battery,the voltage across the resistor is

As shown in the figure,a straight wire carries a steady current I.A metal bar is in contact with a pair of rails and is in upward motion with velocity of magnitude ν.The polarity of the induced emf in terminals X and Y is

As shown in the figure,a metal bar is in contact with a pair of parallel rails.A steady,uniform,magnetic field B is present directed to the right.The bar is moving upward with velocity of magnitude ν.What is the polarity of the induced emf in terminals X and Y?

A flat coil is in a uniform magnetic field.The magnetic flux through the coil is greatest when the plane of its area is

An outer metal ring surrounds an inner metal ring,as shown in the figure.The current in the outer ring is counterclockwise and decreasing.What is the direction of the induced current in the inner ring?

An ideal step-up transformer doubles a primary voltage of 110 V.What is the ratio of the number of turns in its primary coil to the number of turns in the secondary coil?

A transformer is a device that normally

The area of a rectangular loop of wire is 3.6 × .The loop is placed in a uniform magnetic field that changes steadily from 0.20 T to 1.4 T in 1.6 s.The plane of the loop is perpendicular to the direction of the magnetic field.What is the magnitude of the induced emf in that loop?

A circular coil lies flat on a horizontal surface.A bar magnet is held above the center of the coil with its north pole pointing down.If the magnet is dropped from this position what is the direction of the induced current in the coil,as viewed from above?

The primary coil of an ideal transformer has 100 turns and its secondary coil has 400 turns.If the ac current in the secondary coil is 2 A,what is the current in its primary coil?

A resistor and an inductor are connected in series to an ideal battery of constant terminal voltage.At the moment contact is made with the battery,the voltage across the inductor is

The primary coil of an ideal transformer has 600 turns and its secondary coil has 150 turns.If the current in the primary coil is 2 A,what is the current in its secondary coil?

In the figure,a bar magnet moves away from the solenoid.The direction of the induced current through the resistor R is

A single-turn loop of wire,having a resistance of 8.00 Ω and a cross-sectional area 200 cm2,is perpendicular to a uniform magnetic field that increases steadily from 0.200 T to 2.800 T in 2.20 seconds.What is the magnitude of the induced current in the loop?

What is the self-inductance of an ideal solenoid that is 300 cm long with a cross-sectional area of 1.00 × 10-4 m2 and has 1000 turns of wire? (μ0 = 4π × 10-7 T ∙ m/A)

In an ideal transformer,how many turns are necessary in a 110-V primary if the 24-V secondary has 100 turns?

Introduction to Physics

One-Dimensional Kinematics

Vectors in Physics

Two-Dimensional Kinematics

Newtons Laws of Motion

Applications of Newtons Laws

Work and Kinetic Energy

Potential Energy and Conservation of Energy

Linear Momentum and Collisions

Rotational Kinematics and Energy

Rotational Dynamics and Static Equilibrium

Gravity

Oscillations About Equilibrium

Waves and Sound

Fluids

Temperature and Heat

Phases and Phase Changes

The Laws of Thermodynamics

Electric Charges, Forces, and Fields

Electric Potential and Electric

Electric Current and Direct-Current Circuits

Magnetism

Alternating-Current Circuits

Electromagnetic Waves

Geometrical Optics

Optical Instruments

Physical Optics: Interference and Diffraction

Relativity

Quantum Physics

Atomic Physics

Nuclear Physics and Nuclear Radiation

Filters

A single-turn loop of wire,having a resistance of 8.00 Ω and a cross-sectional area 200 cm²,is perpendicular to a uniform magnetic field that increases steadily from 0.200 T to 2.800 T in 2.20 seconds.What is the magnitude of the induced current in the loop?

What is the self-inductance of an ideal solenoid that is 300 cm long with a cross-sectional area of 1.00 × 10^-4 m² and has 1000 turns of wire? (μ₀ = 4π × 10^-7 T ∙ m/A)