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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 :`Q = int_(t_i)^(t_f) I dt` `=1/R int_(t_i)^(t_f) epsi dt` `= - N/R int_(Phi_i)^(Phi_f) d Phi` `= N/R (Phi_i - Phi_f)` for N= 25 , R=0.50 `Omega, Q = 7.5 xx 10^(-3)` C `Phi_f = 0 , A = 2.0 xx 10^(-4) m^2, Phi_i = 1.5xx10^(-4) Wb` `B= Phi_f//A = 0.75 T` |
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