The resistance of an ideal ammeter is

Two moving coil galvanometers $A$ and $B$ having identical springs are placed in magnetic fields of $0.25 \ T$ and $0.5 \ T$ respectively. If the number of turns in $A$ and $B$ are respectively $36$ and $48$,and the areas of the coils $A$ and $B$ are $2.4 \times 10^{-3} \ m^2$ and $4.8 \times 10^{-3} \ m^2$ respectively,then the ratio of the current sensitivities of the galvanometers $A$ and $B$ is

Two tangent galvanometers $A$ and $B$ are identical except in their number of turns. They are connected in series. On passing a current through them,deflections of $60^{\circ}$ and $30^{\circ}$ are produced. The ratio of the number of turns in $A$ and $B$ is

There are three voltmeters of the same range but of resistances $10000\,\Omega$,$8000\,\Omega$,and $4000\,\Omega$ respectively. The best voltmeter among these is the one whose resistance is ................ $\Omega$.

$A$ galvanometer may be converted into an ammeter or a voltmeter. In which of the following cases will the resistance of the device so obtained be the largest?

The value of shunt resistance,that allows only $10 \%$ of the main current to pass through a galvanometer of resistance $99 \Omega$,is (in $\Omega$)