Question

The resistance of a galvanometer is $2.5\Omega$ and it requires $50mA$ for full scale deflection. The value of shunt resistance required to convert it into an ammeter of range $0$ to $5A$ is

• A. $2.5\times 10^{-2}\Omega$
• B. $0.25\times 10^{-2}\Omega$
• C. $0.025\times 10^{-2}\Omega$
• D. $0.0025\times 10^{-2}\Omega$

Answer 1

Answer: (A)

Here,
Resistance of the galvanometer, $G=2.5\Omega$
Full scale deflection current, $I_8=50mA$
$=50\times 10^{-3}A=0.05A$
To convert the galvanometer into an ammeter of range $0$ to $5Ai.e.I=5A,a$ shunt $S$ is connected in parallel with it such that,
$(I-I_g)S=I_{g}G$
$S=\frac{I_{g}G}{I-I_g}$
$=\frac{0.05\times 2.5}{5-0.05}=0.025\Omega =2.5\times 10^{-2}\Omega$