Question

A galvanometer having a resistance $12\, \Omega$ gives a full scale deflection for a current of 2.5 mA. It is converted into a voltmeter of range 10 V, what is the net resistance of the meter?

• A. $3898\, \Omega$
• B. $3976\, \Omega$
• C. $3988\, \Omega$
• D. $4000\, \Omega$

Answer 1

Answer: (C)

$3988\, \Omega$

Answer 2

Using, $R = \frac{V}{I_g} - G$
Here, $V = 10 \, V, I_g = 2.5 \times 10^{-3} \, A$
and $G = 12 \, \Omega$
$\therefore \:\: R= \frac{10}{2.5 \times 10^{-3} \, A} - 12 = \frac{10^5}{25} - 12$
$R = 4000 - 12 = 3988 \, \Omega$