A wire of length '$$L$$'; having resistance '$$R$$' falls from a height '$$\ell$$' in earth's horizontal magnetic field '$$B$$'. The current through the wire is ( $$\mathrm{g}=$$ acceleration due to gravity)

Two wires '$$\mathrm{A}$$' and '$$\mathrm{B}$$' of equal length are connected in left and right gap respectively of meter bridge, null point is obtained at $$40 \mathrm{~cm}$$, from the left end. Diameters of the wires '$$A$$' and '$$B$$' are in the ratio $$3: 1$$ respectively, the ratio of specific resistance of 'A' to that of 'B' is

A glass cube of length $$24 \mathrm{~cm}$$ has a small air bubble trapped inside. When viewed normally from one face it is $$10 \mathrm{~cm}$$ below the surface. When viewed normally from the opposite face, its apparent distance is $$6 \mathrm{~cm}$$. The refractive index of glass is

What is susceptibility of a medium, if its relative permeability is 0.85?