Question 1

A solenoid of radius 2 cm and length 15 cm has 120 turns.If the rate of change of induced current through it is 12.9 A/s,what is the self-induced emf?

Accepted Answer

A) 2.71 mV 
B) 3.41 mV 
C) 1.96 mV 
D) 4.00 mV 
A) 2.71 mV 
B) 3.41 mV 
C) 1.96 mV 
D) 4.00 mV

Question 2

Hyperthermia is one of the modalities for cancer treatment.In the procedure,the magnetic nanoparticles are injected at the tumor site which is then exposed to radio frequency electromagnetic waves.The radio frequency waves induce oscillations among the magnetic nanoparticles causing their temperature to rise.A modest increase in the temperature at the tumor site (about106S1U1P1$\circ$S1S1P0F)can kill cancer cells.A solenoid is one of the components used for producing the radio frequency waves.If 102 turns of copper wire are used to construct a 10-cm long and 6-cm radius solenoid,what is the indcutance of the solenoid?

Accepted Answer

A) 5.00 mH 
B) 1.48 mH 
C) 9.55 mH 
D) 16.9 mH 
E) 3.89 mH 
A) 5.00 mH 
B) 1.48 mH 
C) 9.55 mH 
D) 16.9 mH 
E) 3.89 mH

Question 3

A single loop of wire with an area of 0.40 m2 is located in the plane of this paper as shown.There is a time-varying magnetic field at the location of the loop.It is directed into the page and its magnitude is given by B = 2T + (3T/s)t.At t = 5.0 s,what is the induced emf in the loop?

Accepted Answer

A) 1.2 V 
B) 1.4 V 
C) 1.7 V 
D) 6.0 V 
E) 6.8 V 
A) 1.2 V 
B) 1.4 V 
C) 1.7 V 
D) 6.0 V 
E) 6.8 V

Question 4

In the circuit shown,what is the time required for the current to reach 63% (= 1 - e-1)of its final value after the switch is closed? R = 500 $\varOmega$ and L = 67 H.

Accepted Answer

A) 0.134 s 
B) 0.440 s 
C) 0.632 s 
D) 2.520 s 
E) 7.463 s 
A) 0.134 s 
B) 0.440 s 
C) 0.632 s 
D) 2.520 s 
E) 7.463 s

Question 5

A 7.2-mH inductor is connected to a current.What is the magnitude of the voltage in the inductor at time t = 3.0 s if the current is I(t)= 5 + 7t -2t2? (Assume two significant digits for each number.)

Accepted Answer

A) 22 mV 
B) 36 mV 
C) 58 mV 
D) 90 mV 
E) 230 mV 
A) 22 mV 
B) 36 mV 
C) 58 mV 
D) 90 mV 
E) 230 mV

Question 6

A metal loop has an area of 0.450 m2 and is placed flat on the ground.There is a uniform magnetic field pointing directly out of the ground.This magnetic field initially has a value of 0.728 T but this decreases to 0.150 T uniformly during a period of 0.238 s.Find the voltage induced in the loop during this time.

Accepted Answer

A) zero 
B) 0.26 V 
C) 1.1 V 
D) 1.7 V 
E) 2.4 V 
A) zero 
B) 0.26 V 
C) 1.1 V 
D) 1.7 V 
E) 2.4 V

Question 7

In the circuit shown,R = 1200 $\varOmega$,L = 6.0 H,and V = 9.0 V.After switch S is closed,how long will it take the current in the inductor to reach 4.0 mA?

Accepted Answer

A) 2.3 ms 
B) 2.7 ms 
C) 3.8 ms 
D) 5.0 ms 
E) 7.7 ms 
A) 2.3 ms 
B) 2.7 ms 
C) 3.8 ms 
D) 5.0 ms 
E) 7.7 ms

Question 8

The long straight wire in the figure has current I = 1 A flowing in it.A square loop which has 10-cm sides is positioned 10 cm away from the wire as shown.The loop is then moved in the positive x-direction with a speed v = 10 cm/s.If the loop has a resistance of 0.02 ohms,calculate the direction and the magnitude of the net force acting on the loop the instant the loop is made to move.

Accepted Answer

A) 3 * 10-7 N to the right 
B) 2 * 10-6 N to the left 
C) 7 * 10-10 N to the right 
D) 5 * 10-14 N to the left 
A) 3 * 10-7 N to the right 
B) 2 * 10-6 N to the left 
C) 7 * 10-10 N to the right 
D) 5 * 10-14 N to the left

Question 9

A supersonic airplane with a wingspan of 10 m is flying over the north magnetic pole (with a magnetic field of 0.5 G perpendicular to the ground)at a speed of three times the speed of sound (Mach 3).What is the potential difference from one end of the wing to the other? Assume that the aircraft wings are made of aluminum.

Accepted Answer

A) 0.25 V 
B) 0.5 V 
C) 0.75 V 
D) 1.0 V 
E) 1.25 V 
A) 0.25 V 
B) 0.5 V 
C) 0.75 V 
D) 1.0 V 
E) 1.25 V

Question 10

How large a current must flow through an L = 1.2 H inductance so that the energy stored is 393 J?

Accepted Answer

A) 1.17 A 
B) 2.31 A 
C) 25.6 A 
D) 44.2 A 
E) 107.1 A 
A) 1.17 A 
B) 2.31 A 
C) 25.6 A 
D) 44.2 A 
E) 107.1 A

Question 11

A circuit consists of a 1-mH inductor connected in series with a 2-$\varOmega$ resistor and a 10-V battery connected for a long time.After the battery is removed from the circuit,how long does it take the current in the circuit to drop to half of its original value?

Accepted Answer

A) 2.4 ms 
B) 1.2 ms 
C) 0.73 ms 
D) 0.35 ms 
E) 0.14 ms 
A) 2.4 ms 
B) 1.2 ms 
C) 0.73 ms 
D) 0.35 ms 
E) 0.14 ms

Question 12

What is the peak voltage generated by a rotating rectangular 4.0 cm by 5.4 cm,68 turn coil in a magnetic field,B= 0.78 T? The coil rotates at 60 Hz.

Accepted Answer

A) 3.4 V 
B) 110 V 
C) 43.2 V 
D) 21.3 V 
E) 55.4 V 
A) 3.4 V 
B) 110 V 
C) 43.2 V 
D) 21.3 V 
E) 55.4 V

Question 13

A metal loop has an area of 0.780 m2 and is placed flat on the ground.Initially there is a uniform magnetic field pointing directly out of the ground of magnitude 0.326 T.This changes uniformly to a magnetic field pointed downward of magnitude 0.114 T during a period of 0.719 s.Find the voltage induced in the loop during this time.

Accepted Answer

A) zero 
B) 0.23 V 
C) 0.25 V 
D) 0.48 V 
E) 0.62 V 
A) zero 
B) 0.23 V 
C) 0.25 V 
D) 0.48 V 
E) 0.62 V

Question 14

An inductor of inductance L and a resistor of resistance R are connected in series.This series combination is then connected across the terminals of a battery.After a very long time,the battery is suddenly removed from the circuit and the circuit is made to form a closed loop so that the current continues to flow.How long after the battery is removed is the current flowing through the resistor equal to half its value before the battery was removed?

Accepted Answer

A) t = L/2R 
B) t = L/R 
C) t = 2L/R 
D) None are correct. 
A) t = L/2R 
B) t = L/R 
C) t = 2L/R 
D) None are correct.

Question 15

Hyperthermia is one of the modalities for cancer treatment.In the procedure,the magnetic nanoparticles are injected at the tumor site which is then exposed to radio frequency electromagnetic waves.The radio frequency waves induce oscillations among the magnetic nanoparticles causing their temperature to rise.A modest increase in the temperature at the tumor site (about106S1U1P1$\circ$S1S1P0F)can kill cancer cells.A solenoid is one of the components used for producing the radio frequency waves.The number of turns of copper wire needed to construct a 10-cm long,6-cm radius,and 5-mH inductance solenoid are

Accepted Answer

A) 188. 
B) 102. 
C) 67. 
D) 42. 
E) 2.1. 
A) 188. 
B) 102. 
C) 67. 
D) 42. 
E) 2.1.

Question 16

An emf of 10 V is applied to a coil with an inductance of 40 mH and a resistance of 0.50 $\varOmega$ .How long does it take for the current to reach one half of its maximum value?

Accepted Answer

A) 0.055 s 
B) 0.55 s 
C) 5.5 s 
D) 55 s 
A) 0.055 s 
B) 0.55 s 
C) 5.5 s 
D) 55 s

Question 17

Which of the following has the largest inductance?

Accepted Answer

A) a solenoid of radius 1cm,length 5 cm,and with 100 turns of wire per centimeter 
B) a solenoid of radius 3cm,length 1 cm,and with 100 turns of wire per centimeter 
C) a solenoid of radius 2cm,length 2 cm,and with 100 turns of wire per centimeter 
D) a solenoid of radius 1cm,length 1 cm,and with 200 turns of wire per centimeter 
E) a solenoid of radius 2 cm,length 5 cm,and with 100 turns of wire per centimeter 
A) a solenoid of radius 1cm,length 5 cm,and with 100 turns of wire per centimeter 
B) a solenoid of radius 3cm,length 1 cm,and with 100 turns of wire per centimeter 
C) a solenoid of radius 2cm,length 2 cm,and with 100 turns of wire per centimeter 
D) a solenoid of radius 1cm,length 1 cm,and with 200 turns of wire per centimeter 
E) a solenoid of radius 2 cm,length 5 cm,and with 100 turns of wire per centimeter

Question 18

What is the inductance of a series RL circuit in which R = 2.0 k$\varOmega$ if the current increases to one third of its final value in 10 $\mu$s?

Accepted Answer

A) 87 mH 
B) 70 mH 
C) 58 mH 
D) 49 mH 
E) 36 mH 
A) 87 mH 
B) 70 mH 
C) 58 mH 
D) 49 mH 
E) 36 mH

Question 19

A long,straight wire is located along the y-axis.The wire carries a current in the +y direction that is changing as a function of time according to I = 3.0 A + (0.20 A/s)t.A loop of wire is located in the x-y plane near the loop as shown in the figure.The loop has dimensions of 7m * 5m and is 1m away from the wire.What is the induced emf in the wire loop at the time t = 4.0 s?

Accepted Answer

A) 4.2 * 10-7 V 
B) 8.3 * 10-7 V 
C) 6.7 * 10-6 V 
D) 7.9 * 10-6 V 
E) 1.3 * 10-5 V 
A) 4.2 * 10-7 V 
B) 8.3 * 10-7 V 
C) 6.7 * 10-6 V 
D) 7.9 * 10-6 V 
E) 1.3 * 10-5 V

Question 20

A 5-turn square loop (0.150 m along a side,resistance = 2.00 $\varOmega$)is placed in a magnetic field that makes an angle of 30S1U1P1$\circ$S1S1P0 with the normal to the plane of the loop.The magnitude of this field varies with time according to B = 2.40t4,where t is measured in s and B in T.What is the induced current in the coil at t = 1.25 s?

Accepted Answer

A) 1.47 A 
B) 1.23 A 
C) 0.913 A 
D) 0.527 A 
E) 0.351 A 
A) 1.47 A 
B) 1.23 A 
C) 0.913 A 
D) 0.527 A 
E) 0.351 A

Exam 29: Electromagnetic Induction

A solenoid of radius 2 cm and length 15 cm has 120 turns.If the rate of change of induced current through it is 12.9 A/s,what is the self-induced emf?

A single loop of wire with an area of 0.40 m2 is located in the plane of this paper as shown.There is a time-varying magnetic field at the location of the loop.It is directed into the page and its magnitude is given by B = 2T + (3T/s)t.At t = 5.0 s,what is the induced emf in the loop?

In the circuit shown,what is the time required for the current to reach 63% (= 1 - e-1)of its final value after the switch is closed? R = 500 Ω\varOmegaΩ and L = 67 H.

A 7.2-mH inductor is connected to a current.What is the magnitude of the voltage in the inductor at time t = 3.0 s if the current is I(t)= 5 + 7t -2t2? (Assume two significant digits for each number.)

In the circuit shown,R = 1200 Ω\varOmegaΩ ,L = 6.0 H,and V = 9.0 V.After switch S is closed,how long will it take the current in the inductor to reach 4.0 mA?

How large a current must flow through an L = 1.2 H inductance so that the energy stored is 393 J?

A circuit consists of a 1-mH inductor connected in series with a 2- Ω\varOmegaΩ resistor and a 10-V battery connected for a long time.After the battery is removed from the circuit,how long does it take the current in the circuit to drop to half of its original value?

What is the peak voltage generated by a rotating rectangular 4.0 cm by 5.4 cm,68 turn coil in a magnetic field,B= 0.78 T? The coil rotates at 60 Hz.

An emf of 10 V is applied to a coil with an inductance of 40 mH and a resistance of 0.50 Ω\varOmegaΩ .How long does it take for the current to reach one half of its maximum value?

Which of the following has the largest inductance?

What is the inductance of a series RL circuit in which R = 2.0 k Ω\varOmegaΩ if the current increases to one third of its final value in 10 μ\muμ s?

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Filters

A single loop of wire with an area of 0.40 m² is located in the plane of this paper as shown.There is a time-varying magnetic field at the location of the loop.It is directed into the page and its magnitude is given by B = 2T + (3T/s)t.At t = 5.0 s,what is the induced emf in the loop?

A 7.2-mH inductor is connected to a current.What is the magnitude of the voltage in the inductor at time t = 3.0 s if the current is I(t)= 5 + 7t -2t²? (Assume two significant digits for each number.)

A circuit consists of a 1-mH inductor connected in series with a 2- $\varOmega$ resistor and a 10-V battery connected for a long time.After the battery is removed from the circuit,how long does it take the current in the circuit to drop to half of its original value?

An emf of 10 V is applied to a coil with an inductance of 40 mH and a resistance of 0.50 $\varOmega$ .How long does it take for the current to reach one half of its maximum value?

What is the inductance of a series RL circuit in which R = 2.0 k $\varOmega$ if the current increases to one third of its final value in 10 $\mu$ s?