Moving Charges and Magnetism - Result Question 78
80. A galvanometer has a coil of resistance $100 ohm$ and gives a full-scale deflection for $30 mA$ current. It is to work as a voltmeter of 30 volt range, the resistance required to be added will be
(a) $900 \Omega$
(b) $1800 \Omega$
(c) $500 \Omega$
(d) $1000 \Omega$
[2010]
(a) $2.4 N$
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Answer:
Correct Answer: 80. (a)
Solution:
- (a) Let the resistance to be added be $R$, then $30=I_g(r+R)$
$ \begin{aligned} & \therefore \quad R=\frac{30}{I_g}-r=\frac{30}{30 \times 10^{-3}}-100 \\ & =1000-100=900 \Omega \end{aligned} $
