Current Electricity 5 Question 14
14. A moving coil galvanometer has 50 turns and each turn has an area $2 \times 10^{-4} m^{2}$. The magnetic field produced by the magnet inside the galvanometer is $0.02 T$. The torsional constant of the suspension wire is $10^{-4} N-m rad^{-1}$. When a current flows through the galvanometer, a full scale deflection occurs, if the coil rotates by $0.2 rad$. The resistance of the coil of the galvanometer is $50 \Omega$. This galvanometer is to be converted into an ammeter capable of measuring current in the range $0-1.0 A$. For this purpose, a shunt resistance is to be added in parallel to the galvanometer. The value of this shunt resistance in ohms, is
Integer Answer Type Questions
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Solution:
- Given, $N=50, A=2 \times 10^{-4} m^{2}, C=10^{-4}, R=50 \Omega$,
$$ B=0.02 T, \theta=0.2 $$
$\operatorname{rad} N i _g A B=C \theta$
$$ \begin{aligned} & \Rightarrow \quad i _g=\frac{C \theta}{N A B}=\frac{10^{-4} \times 0.2}{50 \times 2 \times 10^{-4} \times 0.02}=0.1 A \\ & \therefore \quad V _{a b}=i _g \times G=\left(i-i _g\right) S \Rightarrow 0.1 \times 50=(1-0.1) \times S \end{aligned} $$
