220 Faraday’s LawP31.17In a toroid, all the flux is confined to the inside of thetoroid.BNIrIr==µπ0025002ΦBBdAItadrrzz50020ωmaxsinΦBIatbRR=+FHGIKJ50020maxsinlnεωω=′=FHGIKJ+FHGIKJNddtIaRtBΦ2050020maxlncosFIG. P31.17πω=×+FHGIKJ=−10241050 03770 020 0300 400042247NAAradsmcm4.00 cmV2ejafbg..lncos.costt*P31.18The upper loop has area 0 057 85 10232m maf−. The induced emf in it isεθ=−°××−−NddtBAAdBdtcoscos..1078510215710TsV2.The minus sign indicates that it tends to produce counterclockwise current, to make its ownmagnetic field out of the page. Similarly, the induced emf in the lower loop is×=+×NAdBdtcos...0092509 10222TsVVto producecounterclockwise 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 is5 09 101 57 103 52 1022 2...×−
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