Question

A voltmeter of $250 \,mV$ range having a resistance of $10 \Omega$ is converted into an ammeter of $250 \,mA$ range. The value of necessary shunt is (nearly)

• A. $2 \Omega$
• B. $0.1 \Omega$
• C. $1 \Omega$
• D. $10 \Omega$

Answer 1

Answer: (C)

A voltmeter of $250 \,mV$ range having resistance of $10\, \Omega$
$\therefore V_{g} =G I_{g} $
$\Rightarrow 250 \times 10^{-3} =10 \times I_{g} $
$\Rightarrow I_{g} =25 \times 10^{-3} A $
Shunt required to convert this voltmeter into ammeter.
$S =\frac{G \,I_{g}}{I-I_{g}} $
$=\frac{10 \times\left(25 \times 10^{-3}\right)}{250 \times 10^{-3}-25 \times 10^{-3}}=\frac{10}{9}=1 \,\Omega$