Question

A galvano meter gives a deflection of 55devesion when is shunt s of resistance of 8 ohm is connected in a parallel to it if it produces the deflection of 45 devesions find the resistance of galvano meter

Answer 1

Given:

$I=55$

$I'=45$

$R_{\rm sh}=8\:\Omega$

Total current flowing through the both galvanometer and shunt is 

$$I=I'+I_{\rm sh}$$

For parallel connection of the wires

$$I'R_A=I_{\rm sh}R_{\rm sh}$$

Combining these equations give

$$R_A=\frac{I-I'}{I'}R_{\rm sh}=\frac{55-45}{45}*8\:\Omega=1.78\:\Omega$$