In the conversion of a moving coil galvanometer into an ammeter of a required range,what is the resistance of the ammeter so formed? [$S$ = shunt resistance and $G$ = resistance of the galvanometer]

$A$ galvanometer of resistance $10 \Omega$ changes its range from $1 \text{ mA}$ to $101 \text{ mA}$ when a resistive wire is connected in parallel. If the resistivity of the material of the wire and its area of cross-section are $1 \times 10^{-6} \Omega \text{ m}$ and $1 \text{ mm}^2$ respectively,then the length of the wire is (in $cm$)

$A$ galvanometer of resistance $50 \Omega$ is connected to a battery of $3 \text{ V}$ along with a resistance of $2950 \Omega$ in series,showing a full-scale deflection of $30$ divisions. The additional series resistance required to reduce the deflection to $20$ divisions is: (in $\Omega$)

The resistance of a galvanometer is $90\, \Omega$. If only $10\%$ of the main current is to flow through the galvanometer,how should a resistor be connected and what should be its value?

The deflection in a moving coil galvanometer of resistance $45 \Omega$ falls from $30$ divisions to $3$ divisions. The length of the shunt wire required to convert the galvanometer into an ammeter is [specific resistance of the material of the shunt wire $= 5 \times 10^{-7} \Omega m$ and area of cross-section of the wire $= 4 \times 10^{-7} m^2$]. (in $m$)

What is a shunt? Explain its function in a circuit,obtain the formula for the shunt,and explain its uses.