A particle of mass '$$\mathrm{m}$$' moves along a circle of radius '$$r$$' with constant tangential acceleration. If K.E. of the particle is '$$E$$' by the end of third revolution after beginning of the motion, then magnitude of tangential acceleration is

An e.m.f. $$E=4 \cos (1000 t)$$ volt is applied to an LR circuit of inductance $$3 \mathrm{~mH}$$ and resistance $$4 ~\Omega$$. The maximum current in the circuit is

In the reverse biasing of a p-n junction diode :

When a charge of $$3 ~\mathrm{C}$$ is placed in uniform electric field, it experiences a force of $$3000 \mathrm{~N}$$. Within this field, potential difference between two points separated by a distance of $$1 \mathrm{~cm}$$ is