Chapter 23: Magnetic Flux and Faraday's Law of Induction Selected Solutions

Selected Solutions

19. If the current in the wire changes direction, the direction of the magnetic field is reversed, changing its direction from out of the page to into the page. According to Lenz's law, the current induced in the circuit will oppose this change by flowing counterclockwise, generating a field which is directed out of the page.

27. The current flows clockwise, so the magnetic force is directed to the left. The external force must be equal and opposite the magnetic force to maintain the rod's constant speed. So, it is directed to the right.

33. (a) Only the horizontal component of the magnetic field is important. The vertical component is parallel to the plane of the circular coil at all times. Thus, it does not contribute to the flux through the coil.

(b) Since the emf is given by E = NBAwsin(wt), the maximum emf is

37. (a) From the expression for the inductance of a solenoid, we can solve for the area to get

(b) From Faraday's law written in terms of self-inductance

55. The transformer equation, solved for the primary voltage, gives

In terms of the relationship between the current ratio and turns ratio we have

Selected Solutions by David Reid, Eastern Michigan University. ©2002 by Prentice Hall, Inc.

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