A galvanometer may be converted into ammeter or a voltmeter. In which of the following cases the resistance of the device so obtained will be the largest?
A glass prism ' A ' deviates the red and blue rays through $10^{\circ}$ and $12^{\circ}$ respectively. A second prism ' B ' deviates them through $8^{\circ}$ and $10^{\circ}$ respectively. The ratio of their dispersive powers is (A to B)
In an electric field due to charge $Q$, a charge $q$ moves from point A to B as shown in the figure. The work done is ( $\varepsilon_0=$ permittivity of free space)
An air cored coil has a self inductance 0.1 H . A soft iron core of relative permeability 1000 is introduced and the number of turns is reduced $\left(\frac{1}{10}\right)^{\text {th }}$. The value of self inductance is