Two long parallel wires kept $$2 \mathrm{~m}$$ apart carry $$3 \mathrm{~A}$$ current each, in the same direction. The force per unit length on one wire due to the other is

Which of the following has its permeability less than that of free space?

A square shaped coil of side $$10 \mathrm{~cm}$$, having 100 turns is placed perpendicular to a magnetic field which is increasing at $$1 \mathrm{~T} / \mathrm{s}$$. The induced emf in the coil is

Which one of the following electromagnetic radiation has the least wavelength?