The deflection in moving coil galvanometer of resistance $45 \Omega$ falls from 30 divisions to 3 divisions.…
The deflection in moving coil galvanometer of resistance $45 \Omega$ falls from
30 divisions to 3 divisions. The length of the shunt wire required to convert
galvanometer to ammeter is
[specific resistance of material of shunt wire $=5 \times 10^{-7} \Omega \mathrm{m}$ and area of cross-
section of wire $\left.=4 \times 10^{-7} \mathrm{~m}^{2}\right]$
$4 \mathrm{~m}$
$6 \mathrm{~m}$
$8 \mathrm{~m}$
$2 \mathrm{~m}$
Solution
As per the Question,
$I_{g}=\frac{3}{30} I=\frac{1}{10} I_{,}$
$\Rightarrow\left(I-I_{G}\right) S=I_{G}G$
$\Rightarrow(I-\frac{1}{10} I) S=\frac{1}{10}I G$
$\Rightarrow (\frac{9}{10}) I S$ $=(\frac{1}{10})I G$
$\Rightarrow 9 S=G$
$\therefore G=45 \quad \therefore S=5$
$\therefore S=\frac{S L}{A}$
$\Rightarrow \frac{S A}{S}=L=4 \mathrm{~m}$
.