The coil in a tangent galvanometer is 16 cm in radius. If a current of 20 mA is to produce a deflection of $45{^\circ}$ then the number of turns wound on it, is (Take horizontal component of earth’s magnetic field$= 0.36 imes 10^{- 4}\ T\ and\ \mu_{0} = 4\pi imes 10^{- 7}\ Wb\ A^{- 1}\ m^{- 1}$)

Question

The coil in a tangent galvanometer is 16 cm in radius. If a current of 20 mA is to produce a deflection of $45{^\circ}$ then the number of turns wound on it, is (Take horizontal component of earth’s magnetic field$= 0.36 	imes 10^{- 4}\ T\ and\ \mu_{0} = 4\pi 	imes 10^{- 7}\ Wb\ A^{- 1}\ m^{- 1}$)

Dr. Abubacker · Accepted Answer

(b) Current in coil of tangent galvanometer
$\ \ \ \ \ \ \ \ i = \frac{2rB_{H}}{\mu_{0}n}	an	heta$
$\Longrightarrow \ n = \frac{2rB_{H}}{\mu_{0}i}	an	heta$
$	herefore\ \ \ \ n = \frac{2 	imes 16 	imes 10^{- 2} 	imes 0.36 	imes 10^{- 4}}{4\pi 	imes 10^{- 7} 	imes 20 	imes 10^{- 3}}	an{45{^\circ}}$
$\ \ \ \ \ \ \ \ \ \ \ \  = 458$

Explanation

Reviewed by Dr. Abubacker

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