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Standard XII

Physics

Galvanometer

A moving coil...

Question

A moving coil galvanometer has a coil of area A and number of turns N. A magnetic field B is applied on it. The torque acting on it is given by $τ = k i$ where i is current through the coil. If moment of inertia of the coil is I about the axis of rotation.
If the value of torsional constant if current $i_{0}$ produces angular deflection of $π / 2$ rad is $C = \frac{x N B A i_{0}}{π}$ . Find x.

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Solution

If C is torsional constant of the spring of galvanometer, then:
$τ = C θ$
$N i_{0} A B = C (\frac{π}{2})$
$\Rightarrow C = \frac{2 N B A i_{0}}{π}$

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If C is torsional constant of the spring of galvanometer, then:τ=CθNi0AB=C(π2)⇒C=2NBAi0π

If C is torsional constant of the spring of galvanometer, then:
$τ = C θ$
$N i_{0} A B = C (\frac{π}{2})$
$\Rightarrow C = \frac{2 N B A i_{0}}{π}$