If $\sqrt{A^2+B^2}$ represents the magnitude of resultant of two vectors $(\mathbf{A}+\mathbf{B})$ and $(\mathbf{A}-\mathbf{B})$, then the angle between two vectors is

A thin metal wire of length 'L' and uniform linear mass density '$\rho$' is bent into a circular coil with 'O' as centre. the moment of inertia of a coil about the axis XX' is

The dimensions of torque are same as that of

. For a transistor, the current ratio ' $\beta_{d c}$ ' is defined as the ratio of