Question 1

The magnetic field in the coil is upward and decreasing.The direction of the induced current in the coil,as viewed from the top is

Accepted Answer

A) clockwise. 
B) counterclockwise. 
C) There is no induced current. 
A) clockwise. 
B) counterclockwise. 
C) There is no induced current. B

Question 2

Solenoid two is twice as long and has twice as many turns of wire as solenoid one.Both solenoids have the same cross-sectional area.What is the ratio of the inductance of solenoid two to the inductance of solenoid one?

Accepted Answer

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

Question 3

Which of the following methods will induce a current in a loop of wire in a uniform magnetic field?

Accepted Answer

A) decreasing the strength of the field 
B) rotating the loop about an axis parallel to the field 
C) translating the loop about the field 
D) All are correct. 
E) None are correct. 
A) decreasing the strength of the field 
B) rotating the loop about an axis parallel to the field 
C) translating the loop about the field 
D) All are correct. 
E) None are correct. A

Question 4

If the magnetic field is in the direction as shown,30S1U1P1$\circ$S1S1P0 relative to the x-axis,and has a magnitude of 0.12 T,what is the flux through a circular coil lined up to be perpendicular to the x-axis with a diameter of 2.3 cm?

Accepted Answer

A) 2.3 Tm2 
B) 4.32 * 10-5 Tm2 
C) 34.8 Gm2 
D) 8.35 * 10-4 Gm2 
E) 3900 Tm2 
A) 2.3 Tm2 
B) 4.32 * 10-5 Tm2 
C) 34.8 Gm2 
D) 8.35 * 10-4 Gm2 
E) 3900 Tm2

Question 5

An emf of 10 V is applied to a coil having a resistance of 0.50 $\varOmega$ .If it takes 0.55 s for the current to reach one half of its maximum value,what is the inductance of the coil?

Accepted Answer

A) 229 mH 
B) 312 mH 
C) 397 mH 
D) 40 mH 
A) 229 mH 
B) 312 mH 
C) 397 mH 
D) 40 mH

Question 6

A conducting ring is moving from left to right through a region that contains a constant magnetic field as shown in the diagram.In which regions is there an induced current in the ring?

Accepted Answer

A) regions B and D 
B) regions B,C,and D 
C) region C 
D) All regions have an induced current in the ring. 
A) regions B and D 
B) regions B,C,and D 
C) region C 
D) All regions have an induced current in the ring.

Question 7

The speed of a 15-cm long wire in a 100- mT magnetic field to produce a 3-V motional emf is

Accepted Answer

A) 2 m/s. 
B) 25 m/s. 
C) 41 m/s. 
D) 200 m/s. 
A) 2 m/s. 
B) 25 m/s. 
C) 41 m/s. 
D) 200 m/s.

Question 8

A washer with inner diameter 5.0 cm is carried in your pocket as you walk directly north according to your magnetic compass.Assume the normal to the washer's plane is exactly horizontal,pointing toward magnetic north.The Earth's magnetic field strength is 0.056 mT.If the magnetic flux through the washer's opening is 36 nTm2,what is the angle below local horizontal that the magnetic field vector points?

Accepted Answer

A) 71S1U1P1$\circ$S1S1P0 
B) 19S1U1P1$\circ$S1S1P0 
C) 85S1U1P1$\circ$S1S1P0 
D) 4.7S1U1P1$\circ$S1S1P0 
E) None are correct. 
A) 71S1U1P1$\circ$S1S1P0 
B) 19S1U1P1$\circ$S1S1P0 
C) 85S1U1P1$\circ$S1S1P0 
D) 4.7S1U1P1$\circ$S1S1P0 
E) None are correct.

Question 9

The current in the wire is given by the equation I = 2.5 - 0.6t,with positive to the right as shown.Which of the statements concerning the current induced in the loop is correct?

Accepted Answer

A) There is no induced current. 
B) The current is clockwise always. 
C) The direction of current depends on the value of r. 
D) The current is first clockwise then counterclockwise. 
A) There is no induced current. 
B) The current is clockwise always. 
C) The direction of current depends on the value of r. 
D) The current is first clockwise then counterclockwise.

Question 10

A rectangular (45 cm long by 22 cm wide)circuit loop with resistance 35 $\varOmega$ is held parallel to the xy-plane with one end inside a uniform magnetic field.The magnetic field for x  0 the magnetic field is zero.Initially the left end of the loop is at x = -30 cm and the right end is at x = 15cm.Calculate the magnitude of the force required to move the loop to the right along the positive x-axis at a constant speed of 13 cm/s while the left end of the loop is still in the magnetic field.

Accepted Answer

A) 5.8 * 10-4 N 
B) 3.2 * 10-4 N 
C) 1.5 * 10-3 N 
D) 1.6 * 10-2 N 
E) 2.0 * 10-2 N 
A) 5.8 * 10-4 N 
B) 3.2 * 10-4 N 
C) 1.5 * 10-3 N 
D) 1.6 * 10-2 N 
E) 2.0 * 10-2 N

Question 11

Which of the following will not produce an induced potential difference in a loop of copper wire in the presence of a uniform and constant magnetic field?

Accepted Answer

A) The loop moves in a straight line but does not rotate. 
B) The loop rotates but does not move in a straight line. 
C) The loop both moves in a straight line and rotates. 
D) None are correct. 
A) The loop moves in a straight line but does not rotate. 
B) The loop rotates but does not move in a straight line. 
C) The loop both moves in a straight line and rotates. 
D) None are correct.

Question 12

A 15-mH inductor is connected in series with a battery and a 12-$\varOmega$ resistor,in a circuit with an open switch.0.50 ms after the switch is closed,the current in the circuit is 1.2A. What is the EMF supplied by the battery?

Accepted Answer

A) 44 V 
B) 21 V 
C) 3.6 V 
D) 1.8 V 
A) 44 V 
B) 21 V 
C) 3.6 V 
D) 1.8 V

Question 13

When the switch in the circuit below is closed,what will happen?

Accepted Answer

A) The current will start at I = V/R in the direction shown and then drop to zero. 
B) The current will gradually rise to I = V/R in the direction shown. 
C) The current will rise slowly to a final value of I = RL. 
D) No current will flow. 
E) The current will gradually rise to I = V/R in the direction opposite to that shown. 
A) The current will start at I = V/R in the direction shown and then drop to zero. 
B) The current will gradually rise to I = V/R in the direction shown. 
C) The current will rise slowly to a final value of I = RL. 
D) No current will flow. 
E) The current will gradually rise to I = V/R in the direction opposite to that shown.

Question 14

A long solenoid of length 2.0 m and n=300 turns/m carries a current of 4.0 A.It stores an energy of 3.4 J.What is the cross sectional area of the solenoid?

Accepted Answer

A) 0.70 m2 
B) 1.2 m2 
C) 1.4 m2 
D) 1.7 m2 
E)   1.9 m2  
A) 0.70 m2 
B) 1.2 m2 
C) 1.4 m2 
D) 1.7 m2 
E)   1.9 m2

Question 15

A 2.0 m long solenoid of cross sectional area 1.4 m2 and 300 turns/m carries a current.It stores an energy of 3.4 J.What is the current in the solenoid?

Accepted Answer

A) 4.3 A 
B) 4.0 A 
C) 5.2 A 
D) 4.9 A 
E) 4.6 A 
A) 4.3 A 
B) 4.0 A 
C) 5.2 A 
D) 4.9 A 
E) 4.6 A

Question 16

How much energy is stored in a long solenoid with 660 turns,length L = 3.2 m,and a cross sectional area A = 121 cm2,when the current in it is I = 85 A?

Accepted Answer

A) 1.1 mJ 
B) 9.11 kJ 
C) 1.1 kJ 
D) 5.21 J 
E) 7.48 J 
A) 1.1 mJ 
B) 9.11 kJ 
C) 1.1 kJ 
D) 5.21 J 
E) 7.48 J

Question 17

A solenoid of cross sectional area 1.4 m2 and 2.0 m long carries a current of 4.0 A.It stores an energy of 3.4 J.How many turns per unit length are in this solenoid?

Accepted Answer

A) 390 turns/m 
B) 300 turns/m 
C) 450 turns/m 
D) 420 turns/m 
E)   350 turns/m 
A) 390 turns/m 
B) 300 turns/m 
C) 450 turns/m 
D) 420 turns/m 
E)   350 turns/m

Question 18

An RL circuit with a resistor with R = 8.80 $\varOmega$ and an inductor with inductance L = 3.70 mH has an energy of 3.00 J with the switch in position a.At time = 0 seconds,the switch is moved to position b.What is the current (in a)after 1.90 milliseconds?

Accepted Answer

A) 0.321 
B) 0.375 
C) 0.439 
D) 0.514 
E) 0.601 
A) 0.321 
B) 0.375 
C) 0.439 
D) 0.514 
E) 0.601

Question 19

The external magnetic field in a loop decreases from 0.1 Tesla to zero in 2 seconds.The loop of wire has ten turns,a radius of 10 cm,with its axis 45 degrees relative to the magnetic field.How large is the induced voltage in the loop?

Accepted Answer

A) 0 mV 
B) 11 mV 
C) 9.4 mV 
D) 32.5 mV 
E) 0.31 mV 
A) 0 mV 
B) 11 mV 
C) 9.4 mV 
D) 32.5 mV 
E) 0.31 mV

Question 20

A circular wire loop of resistance R = 1.0 $\varOmega$ and diameter 5.0 cm rotates with period 150 ms about a horizontal axis while in a region having a 0.142 T magnetic field pointing in a horizontal plane at an angle of 35 degrees relative to the rotation axis.At time t = 0 the plane of the loop is horizontal.What is the magnitude of the induced EMF in the loop at a time of t = 75ms?

Accepted Answer

A) 4.7 mV 
B) 0.75 mV 
C) 6.7 mV 
D) 0 
E) 8.2 mV 
A) 4.7 mV 
B) 0.75 mV 
C) 6.7 mV 
D) 0 
E) 8.2 mV

Exam 29: Electromagnetic Induction

The magnetic field in the coil is upward and decreasing.The direction of the induced current in the coil,as viewed from the top is

Solenoid two is twice as long and has twice as many turns of wire as solenoid one.Both solenoids have the same cross-sectional area.What is the ratio of the inductance of solenoid two to the inductance of solenoid one?

Which of the following methods will induce a current in a loop of wire in a uniform magnetic field?

If the magnetic field is in the direction as shown,30 ∘\circ∘ relative to the x-axis,and has a magnitude of 0.12 T,what is the flux through a circular coil lined up to be perpendicular to the x-axis with a diameter of 2.3 cm?

An emf of 10 V is applied to a coil having a resistance of 0.50 Ω\varOmegaΩ .If it takes 0.55 s for the current to reach one half of its maximum value,what is the inductance of the coil?

A conducting ring is moving from left to right through a region that contains a constant magnetic field as shown in the diagram.In which regions is there an induced current in the ring?

The speed of a 15-cm long wire in a 100- mT magnetic field to produce a 3-V motional emf is

The current in the wire is given by the equation I = 2.5 - 0.6t,with positive to the right as shown.Which of the statements concerning the current induced in the loop is correct?

Which of the following will not produce an induced potential difference in a loop of copper wire in the presence of a uniform and constant magnetic field?

A 15-mH inductor is connected in series with a battery and a 12- Ω\varOmegaΩ resistor,in a circuit with an open switch.0.50 ms after the switch is closed,the current in the circuit is 1.2A. What is the EMF supplied by the battery?

When the switch in the circuit below is closed,what will happen?

A long solenoid of length 2.0 m and n=300 turns/m carries a current of 4.0 A.It stores an energy of 3.4 J.What is the cross sectional area of the solenoid?

A 2.0 m long solenoid of cross sectional area 1.4 m2 and 300 turns/m carries a current.It stores an energy of 3.4 J.What is the current in the solenoid?

How much energy is stored in a long solenoid with 660 turns,length L = 3.2 m,and a cross sectional area A = 121 cm2,when the current in it is I = 85 A?

A solenoid of cross sectional area 1.4 m2 and 2.0 m long carries a current of 4.0 A.It stores an energy of 3.4 J.How many turns per unit length are in this solenoid?

An RL circuit with a resistor with R = 8.80 Ω\varOmegaΩ and an inductor with inductance L = 3.70 mH has an energy of 3.00 J with the switch in position a.At time = 0 seconds,the switch is moved to position b.What is the current (in a)after 1.90 milliseconds?

The external magnetic field in a loop decreases from 0.1 Tesla to zero in 2 seconds.The loop of wire has ten turns,a radius of 10 cm,with its axis 45 degrees relative to the magnetic field.How large is the induced voltage in the loop?

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Filters

An emf of 10 V is applied to a coil having a resistance of 0.50 $\varOmega$ .If it takes 0.55 s for the current to reach one half of its maximum value,what is the inductance of the coil?

A 15-mH inductor is connected in series with a battery and a 12- $\varOmega$ resistor,in a circuit with an open switch.0.50 ms after the switch is closed,the current in the circuit is 1.2A. What is the EMF supplied by the battery?

A 2.0 m long solenoid of cross sectional area 1.4 m² and 300 turns/m carries a current.It stores an energy of 3.4 J.What is the current in the solenoid?

How much energy is stored in a long solenoid with 660 turns,length L = 3.2 m,and a cross sectional area A = 121 cm²,when the current in it is I = 85 A?

A solenoid of cross sectional area 1.4 m² and 2.0 m long carries a current of 4.0 A.It stores an energy of 3.4 J.How many turns per unit length are in this solenoid?