The equation of the tangent to the curve $y=\mathrm{be}^{-x / \mathrm{a}}$ at the point where it crosses the Y axis is

The magnetic moment of electron due to orbital motion is proportional to ( $\mathrm{n}=$ principal quantum number)

A same torque is applied to a disc and a ring of equal mass and radii then

A capacitor of unknown capacity is connected across a battery of V volt. The charge stored in it is Q coulomb. When potential across the capacitor is reduced by $\mathrm{V}_1$ volt, the charge stored in it becomes $\mathrm{Q}_1$ coulomb. The potential V is