You hold a bar magnet, aligned as shown in the diagram, some distance from the c

Question

You hold a bar magnet, aligned as shown in the diagram, some distance from the center of a loop of wire. The magnetic field of the bar magnet at the center of the loop is 0.15 T. Then you move it rapidly towards the loop. At the new location, the magnetic field of the bar magnet at the center of the loop is 0.35 T. Your lab partner times your motion and reports that it took you 0.25 seconds to move the magnet. The radius of the loop is 3.5 cm. a. While you are moving the magnet, what is the direction of the electric field in the copper loop at location P? b. Approximately what is the emf in the loop while you are moving the magnet? Show all steps in your work

Explanation / Answer

From the Lenz law , the induced current always opposes the induces emf

so the direction of eelectric field at point p is counter clock wise

(b)

induced emf is = d pi/ dt

                         = A dB/dt

                        = pi r^2 ( Bf - Bi)/dt

                       = pi ( 0.035 m)^2 ( 0.35 T - 0.15 T)/ 0.25 s

                      = 3.07 mV or 3.07 * 10 ^-3 V

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