Question 270: Current Electricity

Question

A moving coil galvanometer allows a full scale
current of 10–4 A. A series resistance of 2 M$$\Omega $$
is required to convert the above galvanometer
into a voltmeter of range 0-5 V. Therefore the
value of shunt resistance required to convert the
above galvanometer into an ammeter of range
0.10 mA is :

Accepted Answer

Given data,
$$
\begin{aligned}
I  =10^{-4} \mathrm{~A}, \\
R_S  =2 \mathrm{M} \Omega=2 	imes 10^6 \Omega, \\
V_{\max }  =5 \mathrm{~V}
\end{aligned}
$$
Let internal resistance of galvanometer is $R_G$.
Then,
$$
\begin{array}{lc} 
 I 	imes R_S+I 	imes R_G=V_{\max } \\
\Rightarrow  2 	imes 10^6 	imes 10^{-4}+10^{-4} 	imes R_G=5 \\
\Rightarrow  10^{-4} R_G=5-200=-195 \\
	ext { or }  R_G=-195 	imes 10^4 \Omega
\end{array}
$$
Resistance cannot be negative.
$	herefore$ No option is correct.

Answer

200 $$\Omega $$

Answer

500 $$\Omega $$

Answer

100 $$\Omega $$

Answer

None of the options are correct

Current Electricity

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