Question

A galvanometer of 25 ohms and having full scale deflection for a current of 10 mA is changed into voltmeter of range 100 volts by connecting a resistance R in series with the galvanometer. The resistance R in ohms is:

• A. 10000
• B. 975
• C. 10025
• D. 9975

Answer 1

Answer: (D)

9975

Answer 2

Using formula for resistance R $R=\frac{V}{{{i}_{g}}}-G$ Here, $G=25\,\Omega ,$ ${{i}_{g}}=10\times {{10}^{-3}}A,$ $V=100\,V$ On putting the value in above formula, we get $=\frac{100}{10\times {{10}^{-3}}}-25$ $=1000-25$ $=9975\,ohm$