What is the shape of the magnet in a moving coil galvanometer used to create a radial magnetic field?

The deflection in a moving coil galvanometer is

In a moving coil galvanometer,the deflection of the coil $\theta$ is related to the electrical current $i$ by the relation

When a $12\,\Omega$ resistor is connected in parallel with a moving coil galvanometer,its deflection reduces from $50$ divisions to $10$ divisions. The resistance of the galvanometer is ............. $\Omega$.

To convert a galvanometer into an ammeter,one needs to connect a

$A$ voltmeter of resistance $20000\,\Omega$ reads $5 \text{ V}$. To make it read $20 \text{ V}$,the extra resistance required is