If only $\frac{1}{51}^{th}$ ot the main current is to be passed through a galvanometer then the shunt required is $R_1$ and if only $\frac{1}{11}^{th}$ of the main voltage is to be developed across the galvanometer, then the resistance required is $R_2$. Then $\frac{R_2}{R_1} =$
If only $\frac{1}{51}$ th of the main current $i$ is to be passed through galvanometer $G$ then the shunt required is main current, $i=51$ $ i_{g}=1 $ $ \therefore R_{1}=\frac{G}{i-i_{9}} $ $\Rightarrow R_{1}=\frac{G}{51-1}=\frac{G}{50} \,\,\,\,\,....(i)$
If only $\frac{1}{11} th$ of the main voltage is developed across the $G$ then the resistance required, $R_{2}$. $R_{2}=G\left(V_{G}-1\right)$ $R_{2}=G(11-1)=10 G\,\,\,\,\,\,\,\,\dots(ii)$ Now, from Eqn. (i) and (ii), we get $\frac{R_{2}}{R_{1}}=\frac{10 G}{\frac{G}{50}}=500 $ $\therefore \frac{R_{2}}{R_{1}}=500$
There are various electrical instruments used to measure current, power, voltage, etc. Some of them are briefly explained below:
Moving Coil Galvanometer
It is an electromagnetic device which measures small values of current.
Its working principle is that whenever a current loop is placed in a magnetic field, it experiences a certain torque. The value of that torque can be modified by modifying the current in the loop.
For a current carrying loop having N turns, and cross sectional area A, carrying current i, whenever it is placed in and along the direction of an external magnetic field B, it experiences a torque given by:
