Question

A galvanometer, with a scale divided into $150$ equal divisions, has current sensitivity of $10$ divisions per milliampere and voltage sensitivity of $2$ divisions per millivolt. Find shunt resistance for making an ammeter of $6A$ .

• A. $1.25 \, \times \, 10^{- 3} \, \Omega $
• B. $12.5 \, \times \, 10^{- 3} \, \Omega $
• C. $125 \, \times \, 10^{- 3} \, \Omega $
• D. $0.125 \, \times \, 10^{- 3} \, \Omega $

Answer 1

Answer: (B)

$\left.\begin{array}{l}I_{g}=15 \mathrm{~mA} \\ V_{g}=75 \mathrm{mV} \\ I=6 \mathrm{~A}\end{array}\right\} \Rightarrow R_{g}=\frac{V_{g}}{I_{g}}=5 \Omega$
$S \, = \, \frac{I_{g} R_{g}}{I - I_{g}}=12.5 \, \times \, 10^{- 3} \, \Omega $