Exam 29: Electromagnetic Induction

The three loops of wire shown in the figure are all subject to the same uniform magnetic field that does not vary with time.Loop 1 oscillates back and forth as the bob in a pendulum,loop 2 rotates about a vertical axis,and loop 3 oscillates up and down at the end of a spring.Which loop,or loops,will have an emf induced in them?

In the figure,the inner loop carries a clockwise current I that is increasing.The resistor R is in the outer loop and both loops are in the same plane.The induced current through the resistor R is

In the figure,a straight wire carries a current I.The wire passes through the center of a toroidal coil.If the current in the wire is quickly reduced to zero,the induced current through the resistor R is

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

In the figure,two parallel wires carry currents of magnitude I in opposite directions.A rectangular loop is midway between the wires.The current I is decreasing with time.The induced current through the resistor R is

In the figure,two solenoids are approaching each other with speed v as shown.The induced current through the resistor R is

A loop of radius r = 3.0 cm is placed parallel to the xy-plane in a uniform magnetic field = 0.75 T .The resistance of the loop is 18 Ω.Starting at t = 0,the magnitude of the field decreases uniformly to zero in 0.15 seconds.What is the magnitude of the electric current produced in the loop during that time?

A conducting bar moves along frictionless conducting rails connected to a 4.00-Ω resistor as shown in the figure.The length of the bar is 1.60 m and a uniform magnetic field of 2.20 T is applied perpendicular to the paper pointing outward,as shown. (a)What is the applied force required to move the bar to the right with a constant speed of 6.00 m/s? (b)At what rate is energy dissipated in the 4.00 Ω resistor?

In the figure,a copper bar is in contact with a pair of parallel metal rails and is in motion with velocity ν.A uniform magnetic field is present pointing downward,as shown.The bar,the rails,and the resistor R are all in the same plane.The induced current through the resistor R is

A uniform magnetic field is applied perpendicular to the plane of a 60-turn circular coil with a radius of 6.0 cm and a resistance of 0.60 Ω.If the magnetic field increases uniformly from 0.20 T to 1.8 T in 0.20 s,what is the magnitude of the emf induced in the coil?

A 200-loop coil of cross sectional area 8.5 cm² lies in the plane of the page.An external magnetic field of 0.060 T is directed out of the plane of the page.The external field decreases to 0.020 T in 12 milliseconds. (a)What is the magnitude of the change in the external magnetic flux enclosed by the coil? (b)What is the magnitude of the average voltage induced in the coil as the external flux is changing? (c)If the coil has a resistance of 4.0 ohms,what is the magnitude of the average current in the coil?

A ten-loop coil having an area of 0.23 m² and a very large resistance is in a 0.047-T uniform magnetic field oriented so that the maximum flux goes through the coil.The coil is then rotated so that the flux through it goes to zero in 0.34 s.What is the magnitude of the average emf induced in the coil during the 0.34 s?

A capacitor is charging in a simple RC circuit with a dc battery.Which one of the following statements about this capacitor is accurate?

A large magnetic flux change through a coil must induce a greater emf in the coil than a small flux change.

The long straight wire in the figure carries a current I that is decreasing with time at a constant rate.The circular loops A,B,and C all lie in a plane containing the wire.The induced emf in each of the loops A,B,and C is such that

The figure shows a bar magnet moving vertically upward toward a horizontal coil.The poles of the bar magnets are labeled X and Y.As the bar magnet approaches the coil it induces an electric current in the direction indicated on the figure (counter-clockwise as viewed from above).What are the correct polarities of the magnet?

The coil in a 60-Hz ac generator has 125 turns,each having an area of 3.0 × 10^-2 m² and is rotated in a uniform 0.12-T magnetic field.What is the peak output voltage of this generator?

A bar magnet is held vertically with its upper end a little bit below the center of a horizontal metal ring.The upper end of the magnet is its north pole,as shown in the figure.The bar magnet is now dropped.An observer views the ring from above its center.To this observer,how will the induced current in the ring behave as the magnet falls?

A circular loop of wire lies in the plane of the paper.An increasing magnetic field points out of the paper.What is the direction of the induced current in the loop?

You are designing a generator to have a maximum emf of 8.0 V.If the generator coil has 200 turns and a cross-sectional area of 0.030 m²,what should be the frequency of the generator in a uniform magnetic field of 0.030 T?