$A$ small cylindrical soft iron piece is kept in a galvanometer so that

$A$ moving coil galvanometer has $100$ turns and each turn has an area of $2.0 \,cm^2$. The magnetic field produced by the magnet is $0.01 \,T$ and the deflection in the coil is $0.05$ radian when a current of $10 \,mA$ is passed through it. The torsional constant of the suspension wire is $x \times 10^{-5} \,N-m / rad$. The value of $x$ is . . . . . . .

In a moving coil galvanometer,two moving coils $M_1$ and $M_2$ have the following particulars:
$R_1 = 5 \ \Omega, N_1 = 15, A_1 = 3.6 \times 10^{-3} \ m^2, B_1 = 0.25 \ T$
$R_2 = 7 \ \Omega, N_2 = 21, A_2 = 1.8 \times 10^{-3} \ m^2, B_2 = 0.50 \ T$
Assuming that the torsional constant of the springs is the same for both coils,what will be the ratio of the voltage sensitivity of $M_1$ and $M_2$?

$A$ galvanometer having a coil of resistance $30 \ \Omega$ needs $20 \ \text{mA}$ of current for full-scale deflection. If a maximum current of $3 \ \text{A}$ is to be measured using this galvanometer,the resistance of the shunt to be added to the galvanometer should be $\frac{30}{X} \ \Omega$,where $X$ is

$A$ moving coil galvanometer of resistance $100 \ \Omega$ shows full-scale deflection when a current of $100 \ \mu A$ passes through it. If it is intended to show full-scale deflection when a current of $1 \ mA$ passes through it,the value of shunt resistance in ohms to be connected to the galvanometer is:

If only $5 \%$ of the total current is to be passed through a galvanometer of resistance $G$,then the resistance of the shunt will be