Question

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

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

Answer 1

Answer: (C)

$0.03 \, \Omega$

Answer 2

Given : $V = 750 \times 10^{-3} V;$
$I_{g} = 15 \times 10^{-3} A$
and $I = 25\, A$
Using therelation
$a = \frac{Y}{I_{g}}$
$= \frac{750\times 10^{-3}}{15\times 10^{-3}}$
$= 50\, \Omega$
$I_{g} = \frac{S}{S + a}\times I$
$15\times 106-3 = \left(\frac{S}{S + 50}\right) \times 25$
$\therefore \, \, S = 0.03\, \Omega$