Q.

A moving coil galvanometer has 100 turns and each turn has an area of 2.0 cm². The magnetic field produced by the magnet is 0.01 T and the deflection in the coil is 0.05 radian when a current of 10 mA is passed through it. The torsional constant of the suspension wire is x×10-5 N-m/rad. The value of x is _____.                                 [2024]


Ans.

(4)      Given,B=0.01T,i=10mA,N=100

           A=2×10-4m2:K=?

           τ=Kθ                                           (i)

           τ=BiNAsinϕ                            (ii)

          From (i) and (ii),Kθ=BiNAsin90°

          K=BiNAθ

         K=(0.01)×(10×10-3A)×(100)×(2×10-4m2)(0.05)

         K=2×10-45=205×10-5=4×10-5N-m/rad

         x=4