Question

The resistance of a galvanometer is 199 . The sensitiveness is $2\times {10}^{-4}$ A per division. The scale contains 100 divisions. In order to convert it into an ammeter to read upto 4 A, the shunt resistance is

• A. 0.5
• B. 1
• C. 2
• D. 3.5

Answer 1

The correct option is B 1

$i_g$ for one division $=2\times {10}^{-4}A$

$S=\frac{i_{g}G}{(i-i_g)}$

So $i_g$ for 100 divisions $=2\times {10}^{-4}\times 100A$

$=2\times {10}^{-2}A$

$S=\frac{i_{g}G}{(i-i_g)}$

$=\frac{2\times {10}^{-2}\times 199}{4-2\times {10}^{-2}}$

$=$1 ohm