Question 1

The magnetic flux through a loop is made to vary according to the relation   where the units are SI.The EMF induced in the loop when t = 2 s is

Accepted Answer

A) 38 V 
B) 39 V 
C) 40 V 
D) 31 V 
E) 19 V 
A) 38 V 
B) 39 V 
C) 40 V 
D) 31 V 
E) 19 V

Question 2

A 3.0-cm by 5.0-cm rectangular coil has 100 turns.Its axis makes an angle of 55º with a uniform magnetic field of 0.35 T.What is the magnetic flux through this coil?

Accepted Answer

A) 3.0 $\times$ 10-4 Wb 
B) 4.3 $\times$ 10-4 Wb 
C) 3.0 $\times$ 10-2 Wb 
D) 4.3 $\times$ 10-2 Wb 
E) 5.3 $\times$ 10-2 Wb 
A) 3.0 $\times$ 10-4 Wb 
B) 4.3 $\times$ 10-4 Wb 
C) 3.0 $\times$ 10-2 Wb 
D) 4.3 $\times$ 10-2 Wb 
E) 5.3 $\times$ 10-2 Wb

Question 3

A coil consisting of 20 turns of wire around the periphery of a rectangular frame 10 cm by 5.0 cm is moved from a position near a magnet where the average flux density is 1.0 mT to another position where the average is 11 mT.If this motion takes place in
1.0 s,the average EMF induced in the coil is

Accepted Answer

A) 0.10 kV 
B) 1.0 kV 
C) 1.0 mV 
D) 0.10 MV 
E) 10 mV 
A) 0.10 kV 
B) 1.0 kV 
C) 1.0 mV 
D) 0.10 MV 
E) 10 mV

Question 4

The magnetic flux through a certain coil is given by   where the units are SI.The coil has 100 turns.The magnitude of the induced EMF when t = 1/200 s is

Accepted Answer

A) 100 V 
B) 200 V 
C) zero 
D) 2/$\pi$ V 
E) 1/50$\pi$ V 
A) 100 V 
B) 200 V 
C) zero 
D) 2/$\pi$ V 
E) 1/50$\pi$ V

Question 5

Use the following figure for the next problem.  
-A rectangular coil moving at a constant speed v enters a region of uniform magnetic field from the left.While the coil is entering the field,the direction of the magnetic force is

Accepted Answer

A) 1 
B) 2 
C) 3 
D) 4 
E) 5 
A) 1 
B) 2 
C) 3 
D) 4 
E) 5

Question 6

Two identical bar magnets are dropped from equal heights.Magnet A is dropped over bare earth and magnet B over a metal plate.Which magnet strikes first?

Accepted Answer

A) magnet A 
B) magnet B 
C) both strike at the same time 
D) whichever has its N pole toward the ground 
E) whichever has its S pole toward the ground 
A) magnet A 
B) magnet B 
C) both strike at the same time 
D) whichever has its N pole toward the ground 
E) whichever has its S pole toward the ground

Question 7

The instantaneous induced EMF in a coil of wire located in a magnetic field

Accepted Answer

A) depends on the time rate of change of flux through the coil. 
B) depends on the instantaneous value of flux through the coil. 
C) is independent of the area of the coil. 
D) is independent of the number of turns of the coil. 
E) is determined by the resistance in series with the coil. 
A) depends on the time rate of change of flux through the coil. 
B) depends on the instantaneous value of flux through the coil. 
C) is independent of the area of the coil. 
D) is independent of the number of turns of the coil. 
E) is determined by the resistance in series with the coil.

Question 8

A metal disk rotates about its central axis at an angular frequency of 800 radians per second in a uniform magnetic field of 0.8 T.The diameter of the disk is 8 cm.What is the magnitude of the voltage difference between the center and edge of the disk?

Accepted Answer

A) 0 V 
B) 0.80 V 
C) 0.51 V 
D) 1.0 V 
E) 3.1 V 
A) 0 V 
B) 0.80 V 
C) 0.51 V 
D) 1.0 V 
E) 3.1 V

Question 9

An LR circuit has a resistance R = 25 $\Omega$,an inductance L = 5.4 mH,and a battery of EMF = 9.0 V.How much energy is stored in the inductance of this circuit when a steady current is achieved?

Accepted Answer

A) zero 
B) 0.35 J 
C) 0.35 mJ 
D) 0.70 mJ 
E) 0.97 mJ 
A) zero 
B) 0.35 J 
C) 0.35 mJ 
D) 0.70 mJ 
E) 0.97 mJ

Question 10

A 100-turn coil has a radius of 7.50 cm and a resistance of 50.0 $\Omega$.At what rate must a perpendicular magnetic field change to produce a current of 5.00 A in the coil?

Accepted Answer

A) 275 T/s 
B) 134 T/s 
C) 329 T/s 
D) 141 T/s 
E) 106 T/s 
A) 275 T/s 
B) 134 T/s 
C) 329 T/s 
D) 141 T/s 
E) 106 T/s

Question 11

You place a single loop of wire 0.50 m by 0.30 m perpendicular to a field of 2.0 T.In 30 ms you turn the loop until it is parallel with the field.The average emf induced in this loop is

Accepted Answer

A) 0.30 V 
B) 10 V 
C) 5.0 V 
D) 67 V 
E) 20 V 
A) 0.30 V 
B) 10 V 
C) 5.0 V 
D) 67 V 
E) 20 V

Question 12

A region of space contains a magnetic field of 500 G and an electric field of 3 $\times$ 106 N/C.The total energy density in a cubical box of side   = 20 cm in this region is

Accepted Answer

A) 19.4 kJ/m3  
B) 12.2 kJ/m3  
C) 1.03 kJ/m3  
D) 66.9 J/m3  
E) 24.6 J/m3  
A) 19.4 kJ/m3  
B) 12.2 kJ/m3  
C) 1.03 kJ/m3  
D) 66.9 J/m3  
E) 24.6 J/m3

Question 13

How much does the energy stored in an inductor change if the current through the inductor is doubled?

Accepted Answer

A) it is the same 
B) it is doubled 
C) it is quadrupled 
D) it is halved 
E) it is quartered 
A) it is the same 
B) it is doubled 
C) it is quadrupled 
D) it is halved 
E) it is quartered

Question 14

After you measure the self-inductance of a coil,you unwind it and then rewind half the length of wire into a coil with the same diameter but half the number of turns.How does this change the self-inductance?

Accepted Answer

A) it is the same 
B) it is doubled 
C) it is quadrupled 
D) it is halved 
E) it is quartered 
A) it is the same 
B) it is doubled 
C) it is quadrupled 
D) it is halved 
E) it is quartered

Question 15

The plane of a circular,200-turn coil of radius 5.25 cm is perpendicular to a uniform magnetic field produced by a large electromagnet.This field is changed at a steady rate from 0.650 T to 0.150 T in 0.0100 s.What is the magnitude of the EMF induced in the coil?

Accepted Answer

A) 110 V 
B) 170 V 
C) 1.7 V 
D) 26 V 
E) 87 V 
A) 110 V 
B) 170 V 
C) 1.7 V 
D) 26 V 
E) 87 V

Question 16

A rectangular coil of length l = 20 cm and width w = 15 cm is moving at a constant speed v = 5 m/s.It enters a region of uniform magnetic field B = 0.2 T from the left.While the coil is completely immersed in the field,the voltage across points a and b is

Accepted Answer

A) 0.20 V 
B) 0.15 V 
C) -0.20 V 
D) -0.15 V 
E) zero 
A) 0.20 V 
B) 0.15 V 
C) -0.20 V 
D) -0.15 V 
E) zero

Exam 28: Magnetic Induction

The magnetic flux through a loop is made to vary according to the relation where the units are SI.The EMF induced in the loop when t = 2 s is

A 3.0-cm by 5.0-cm rectangular coil has 100 turns.Its axis makes an angle of 55º with a uniform magnetic field of 0.35 T.What is the magnetic flux through this coil?

A coil consisting of 20 turns of wire around the periphery of a rectangular frame 10 cm by 5.0 cm is moved from a position near a magnet where the average flux density is 1.0 mT to another position where the average is 11 mT.If this motion takes place in 1.0 s,the average EMF induced in the coil is

The magnetic flux through a certain coil is given by where the units are SI.The coil has 100 turns.The magnitude of the induced EMF when t = 1/200 s is

Use the following figure for the next problem. -A rectangular coil moving at a constant speed v enters a region of uniform magnetic field from the left.While the coil is entering the field,the direction of the magnetic force is

Two identical bar magnets are dropped from equal heights.Magnet A is dropped over bare earth and magnet B over a metal plate.Which magnet strikes first?

The instantaneous induced EMF in a coil of wire located in a magnetic field

A metal disk rotates about its central axis at an angular frequency of 800 radians per second in a uniform magnetic field of 0.8 T.The diameter of the disk is 8 cm.What is the magnitude of the voltage difference between the center and edge of the disk?

An LR circuit has a resistance R = 25 Ω\OmegaΩ ,an inductance L = 5.4 mH,and a battery of EMF = 9.0 V.How much energy is stored in the inductance of this circuit when a steady current is achieved?

A 100-turn coil has a radius of 7.50 cm and a resistance of 50.0 Ω\OmegaΩ .At what rate must a perpendicular magnetic field change to produce a current of 5.00 A in the coil?

You place a single loop of wire 0.50 m by 0.30 m perpendicular to a field of 2.0 T.In 30 ms you turn the loop until it is parallel with the field.The average emf induced in this loop is

A region of space contains a magnetic field of 500 G and an electric field of 3 ×\times× 106 N/C.The total energy density in a cubical box of side = 20 cm in this region is

How much does the energy stored in an inductor change if the current through the inductor is doubled?

After you measure the self-inductance of a coil,you unwind it and then rewind half the length of wire into a coil with the same diameter but half the number of turns.How does this change the self-inductance?

The plane of a circular,200-turn coil of radius 5.25 cm is perpendicular to a uniform magnetic field produced by a large electromagnet.This field is changed at a steady rate from 0.650 T to 0.150 T in 0.0100 s.What is the magnitude of the EMF induced in the coil?

A rectangular coil of length l = 20 cm and width w = 15 cm is moving at a constant speed v = 5 m/s.It enters a region of uniform magnetic field B = 0.2 T from the left.While the coil is completely immersed in the field,the voltage across points a and b is

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Filters

An LR circuit has a resistance R = 25 $\Omega$ ,an inductance L = 5.4 mH,and a battery of EMF = 9.0 V.How much energy is stored in the inductance of this circuit when a steady current is achieved?

A 100-turn coil has a radius of 7.50 cm and a resistance of 50.0 $\Omega$ .At what rate must a perpendicular magnetic field change to produce a current of 5.00 A in the coil?