For a moving coil galvanometer,the deflection | vedclass

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(B) The torque acting on the coil of a moving coil galvanometer is given by $	au = NiAB$,where $N$ is the number of turns,$i$ is the current,$A$ is t

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$1$

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(B) The torque acting on the coil of a moving coil galvanometer is given by $	au = NiAB$,where $N$ is the number of turns,$i$ is the current,$A$ is the area,and $B$ is the magnetic field.The restoring torque provided by the suspension wire is $	au = K	heta$,where $K$ is the torsional constant and $	heta$ is the deflection.Equating the two torques: $NiAB = K	heta$.Rearranging for the area $A$: $A = \frac{K	heta}{NiB}$.Given values:$K = 4.0 	imes 10^{-5}\,Nm\,rad^{-1}$$	heta = 0.05\,rad$$N = 200$$i = 10\,mA = 10 	imes 10^{-3}\,A = 0.01\,A$$B = 0.01\,T$Substituting the values:$A = \frac{4.0 	imes 10^{-5} 	imes 0.05}{200 	imes 0.01 	imes 0.01}$$A = \frac{2.0 	imes 10^{-6}}{0.02} = 1.0 	imes 10^{-4}\,m^2$.Since $1\,m^2 = 10^4\,cm^2$,we have:$A = 1.0 	imes 10^{-4} 	imes 10^4\,cm^2 = 1\,cm^2$.

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