Question

A moving coil instrument has resistance 2$\Omega$ and reads upto 250 V when a resistance 5000$\Omega$ is connected in series with it Find the current range of the instrument when it is used as an ammeter with the coil connected across a shunt resistance of 2 milli ohm

• A. 50 A
• B. 25 A
• C. 100 A
• D. 200 A

Answer 1

The correct option is A 50 A

$V=IR$

therefore current in the series circuit $I=\frac{250}{5000+2}=0.04998A$

current through shunt is $I_{sh}=\frac{I_m{R}_m}{R_{sh}}=\frac{0.04998\times 2}{2\times {10}^{-}3}=49.98A$

current range of instrument $I_m+I_{sh}=49.98+0.04998=50A$