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Unformatted text preview: Phys 122 Introductory Physics II TUTORIAL 7 Magnetism Part 3 Induction, Faradays Law KEY 1. A circular coil (950 turns, radius = 0.060 m) is rotating in a uniform magnetic field. At t = 0 s, the normal to the coil is perpendicular to the magnetic field. At t = 0.010 s, the normal makes an angle of = 45 with the field because the coil has made one-eighth of a revolution. An average emf of magnitude 0.065 V is induced in the coil. Find the magnitude of the magnetic field at the location of the coil. For the circular coil in question, the flux through a single turn changes by = BA cos 45 BA cos 90 = BA cos 45 during the interval of t = 0.010 s . Therefore, for N turns, Faraday's law gives the magnitude of the emf (without the minus sign) as cos 45 Emf = NBA t Since the loops are circular, the area A of each loop is equal to r 2 . Solving for B , we have ( 29 5 2 2 Emf (0.065 V)(0.010 s) 8.6 10 T cos 45 (950) (0.060 m) cos 45 t B N r = = = 2. Parts a and b of the drawing show the same uniform and constant (in time) magnetic field...
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