Question

When a galvanometer is shunted with a 4 ohm resistance the deflection is reduced to one fifth?

Answer 1

Deflection of galvanometer is let say initially equivalent to current "i"

now it is reduced to equivalent current of "i/5" when shunted to 4 ohm resistance

so here since it is parallel resistor

so voltage must be same in both

$V_{shunt} = V_{galvanometer}$

$(i - \frac{i}{5})*4 = \frac{i}{5}* R_g$

here $R_g$ = galvanometer resistance

$\frac{4i}{5}*4 = \frac{i}{5}*R_g$

$R_g = 16 ohm$

so the resistance of galvanometer is 16 ohm

Answer 2

8/3 of the deflection when shunted with 4 ohm only