Question

A galvanometer has current range of $15mA$ and voltage range $750mV$. To convert this galvanometer into an ammeter of range $25A$, the required shunt is

• A. $0.8\Omega$
• B. $0.93\Omega$
• C. $0.03\Omega$
• D. $2.0\Omega$

Answer 1

Answer: (C)

$0.03\Omega$

Given : $V=750\times {10}^{-3}V$;
$I_g=15\times {10}^{-3}A$ and $I=25A$
Using, $a=\frac{y}{I_g}$
$=\frac{750\times {10}^{-3}}{15\times {10}^{-3}}=50\Omega$
$I_g=\frac{S}{S+a}\times I$
$15\times {10}^{-3}=\left(\frac{S}{S+50}\right)\times 25$
$\therefore S=0.03\Omega$