Assertion : The sensitivity of a moving coil galvanometer is increased by placing a suitable magnetic material as a core inside the coil.
Reason : Soft iron has high magnetic permeability and cannot be easily magnetized or demagnetized.
AIIMS 2016, Easy
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Sensitivity of galvanometer
$s\, = \,\frac{\theta }{i} \simeq \frac{{\tan \,\theta }}{i} = \frac{{{\mu _0}N}}{{2R{B_H}}}.$
If a magnetic material is placed inside coil of galvanometer, then
$s\,'\, = \,\frac{{{\mu _r}{\mu _0}N}}{{2R{B_H}}}$
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