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Exam 20: Induced Voltages and Inductance

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Question 21

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A flat coil of wire consisting of 15 turns,each with an area of 40 cm²,is positioned perpendicularly to a uniform magnetic field that increases its magnitude at a constant rate from 1.5 T to 5.1 T in 2.0 s.If the coil has a total resistance of 0.20 Ω,what is the magnitude of the induced current?

A) 7.65E-1 A
B) 5.40E+1 A
C) 5.40E-1 A
D) 8.64E-2 A
E) 2.16E-1 A

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Question 22

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A circular loop (area = 0.20 m²) turns in a uniform magnetic field with B = 0.13 T.At an instant when the angle between the magnetic field and the normal to the plane of the loop is π rads and is decreasing at the rate of 0.50 rad/s,what is the magnitude of the emf induced in the loop?

A) zero
B) 13 mV
C) 26 mV
D) 20 mV

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Question 23

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A coil is rotated in a magnetic field generating an emf given by emf = NBAω sin θ,where θ = ωt.At which angle θ is the emf one-third of its maximum value?

Electricity may be generated by rotating a loop of wire between the poles of a magnet.The induced current is greatest when

A sensitive ammeter is connected to a wire loop and placed within the magnetic field of a strong horseshoe magnet.The ammeter shows a deflection when:

The wiring in a motor has resistance of 1.2 Ω and produces a back emf of 0.62 V when connected to a 10.3-V battery of negligible resistance.Find the current flow through the motor.

An RL series circuit has: 4.8-mH coil,2.8-Ω resistor,1.0-V battery,ammeter and switch.After the switch is closed for a long time,find the final value of the current.

How is the energy stored in a current-carrying inductor related to its self-inductance,L?

A coil is placed in a changing magnetic field and an emf is induced.What happens to the induced emf if the rate of change of magnetic field quadruples?

What is the minimum frequency with which a 300-turn,flat coil of cross sectional area 370 cm² can be rotated in a uniform 25-mT magnetic field if the maximum value of the induced emf is to equal 8.6 V?

What is the self-inductance in a coil that experiences a 2.30-V induced emf when the current is changing at a rate of 160 A/s?

A wire loop of radius 0.250 m is placed in a uniform magnetic field of magnitude 0.740 T. The field is directed perpendicular to the plane of the loop. -If the field reverses its direction,and its magnitude changes to 0.100 T in time 1.06 s,what is the magnitude of the average induced emf in the loop during this time?

According to Lenz's law the direction of an induced current in a conductor will be that which tends to produce which of the following effects?

A planar loop consisting of seven turns of wire,each of which encloses 200 cm²,is oriented perpendicularly to a magnetic field that increases uniformly in magnitude from 14 × 10^-3 T to 38 × 10^-3 T in a time of 8.0 × 10^-3 s.What is the resulting induced current in the coil if the resistance of the coil is 5.0 Ω?

A bar magnet is held above the center of a conducting ring in the horizontal plane.The magnet is dropped so it falls lengthwise toward the center of the ring.Will the falling magnet be attracted toward the ring or be repelled by the ring due to the magnetic interaction of the magnet and the ring?

A series circuit contains a 12-V battery,a 3.3-Ω resistor,and a 4.4-mH inductor.If the switch to the battery is closed at t = 0,find the time required for the current in the circuit to reach 63% of its final value.

The basic function of the electric generator is which of the following conversion processes?

An inductor,battery,resistance,and ammeter and switch are connected in series.If the switch,initially open,is now closed,what is the current's final value?

A straight wire lies along the y-axis initially carrying a current of 10 A in the positive y-direction.The current decreases and reverses to 10 A in the negative y-direction,the change in current happening at a uniform rate.In the 1st quadrant a square conducting coil has 2 sides parallel to the y-axis and the other 2 sides parallel to the x-axis.The side of the coil nearest and parallel to the straight wire is at a distance equal to the length of one of the sides of the square.As the current is going from 10 A in one direction to 10 A in the other,in which direction is the induced current in this side of the square coil nearest to the straight wire?

By what factor is the self-inductance of an air solenoid changed if only its number of coil turns,N,is multiplied by five?