A moving coil galvanometer is converted into an ammeter reading upto 0.03 A by connecting a shunt of resistance 4r across it and into an ammeter reading upto 0.06 A when a shunt of resistance r is connected across it. What is the maximum current which can be sent through this galvanometer, if no shunt is used?

0.02 A

For an ammeter, $\frac{i_{g}}{i}=\frac{S}{G+S}$

$\Rightarrow i_{g} G=\left(i-i_{g}\right) S$

∴ $i_{g} G=\left(0.03-i_{g}\right) 4 r$                   (i)

and $i_{g} G=\left(0.06-i_{g}\right) r$                 (ii)

From eqs. (i) and (ii), we get

$0.12-4 i_{g}=0.06-i_{g}$

Maximum current through the galvanometer, i_g = 0.02 A