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It is desired to measure the magnitude of field between the poles of a powerful loud speaker magnet. A small flat search coil of area 2 "cm"^2 with 25 closely wound turns, is positioned normal to the field direction, and then quickly snatched out of the field region. Equivalently, one can give it a quick 90^@ turn to bring its plane parallel to the field direction). The total charge flown in the coil (measured by a ballistic galvanometer connected to coil) is 7.5 mC. The combined resistance of the coil and the galvanometer is 0.50 Omega. Estimate the field strength of magnet. |
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Answer» Solution :Here initial magnetic flux linked with given coil is, `phi_1=ABcos0^@ "" (because vecA||vecB)` =AB FINAL magnetic flux `phi_2=AB cos 90^@` =0 OR `phi_2=AB cos PHI` =A(0)cos`theta` =0 Induced emf, `epsilon=-N(dphi)/(dt)` `therefore epsilon=-N((phi_2-phi_1)/t)` `=-N((0-AB)/t)` `therefore epsilon="NAB"/t` `therefore IR=(NAB)/t` `therefore (Q/t)R=((NAB)/t)` (Where Q=charge induced in the coil in t TIME ) `therefore B=(QR)/(NA)` `therefore B=((7.5xx10^(-3))(0.5))/((25)(2XX10^(-4))` `therefore` B=0.75 T |
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