If a star emitting yellow light is accelerated towards earth, then to an observer on earth it will appear

The magnitude of the magnetic induction at a point on the axis at a large distance ( $r$ ) from the centre of a circular coil of ' $n$ ' turns and area ' $A$ ' carrying current ( $I$ ) is given by

A metal sphere of radius ' $R$ ' and density ' $\rho_1$ ' is dropped in a liquid of density ' $\sigma$ ' moves with terminal velocity ' $v$ '. Another metal sphere of same radius and density ' $\rho_2$ ' is dropped in the same liquid, its terminal velocity will be

If $\alpha$ is the coefficient of performance of a refrigerator and ' $Q$ ' is heat released to the hot reservoir, then the heat extracted from the cold reservoir ' $Q_2$ ' is