The resistance of an ideal ammeter is

By ammeter,which of the following can be measured?

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

The current sensitivity of a galvanometer can be increased by:
$(A)$ decreasing the number of turns
$(B)$ increasing the magnetic field
$(C)$ decreasing the area of the coil
$(D)$ decreasing the torsional constant of the spring
Choose the most appropriate answer from the options given below.

What is the value of resistance to double the value of number of turns of coil for a galvanometer? Why?

The phosphor bronze strip is used in a moving coil galvanometer because