Question

When a $12\Omega$ resistor is connected in series with a moving coil galvanometer then its deflection reduces from 50 divisions to 10 divisions. The resistance of the galvanometer is

• A. 24 ohm
• B. 36 ohm
• C. 3 ohm
• D. 60 ohm

Answer 1

Answer: (C)

3 ohm

We know that for a galvanometer the deflection is proportional to the current passing through it.

Thus initially , $[V=R_G\ast 50]$
now , when a 12 ohm resistor is connected the equation will become,

$[V=(R_G+12)\ast 10]$

$\left[\right(R_G+12)\ast 10=50\ast R_G]$

$[R_G=3]$ ohm