880_Physics ProblemsTechnical Physics

# 880_Physics ProblemsTechnical Physics - 220 P31.17 Faradays...

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220 Faraday’s Law P31.17 In a toroid, all the flux is confined to the inside of the toroid. B NI r I r == µ π 00 2 500 2 Φ B BdA I t adr r zz 500 2 0 ω max sin Φ B I at bR R = + F H G I K J 500 2 0 max sin ln ε ωω = = F H G I K J + F H G I K J N d dt I a R t B Φ 20 500 2 0m a x ln cos FIG. P31.17 πω + F H G I K J = 10 2 4 10 50 0 377 0 020 0 300 400 0422 4 7 NA A r ads m cm 4.00 cm V 2 ej af bg .. l n cos .c o s t t *P31.18 The upper loop has area 0 05 7 85 10 2 32 m m a f . The induced emf in it is εθ =− ° × × −− N d dt BA A dB dt cos cos . . 1 0 7 8 51 0 2 1 5 71 0 T s V 2 . The minus sign indicates that it tends to produce counterclockwise current, to make its own magnetic field out of the page. Similarly, the induced emf in the lower loop is × =+ × NA dB dt cos . . . 009 2 509 10 2 22 T s V V to produce counterclockwise current in the lower loop, which becomes clockwise current in the upper loop . The net emf for current in this sense around the figure 8 is 5 09 10 1 57 10 3 52 10 22 2 ... ×−
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