A unit step voltage is applied at $$t = 0$$ to a series $$RL$$ circuit with zero initial conditions.

In the series $$RC$$ circuit shown in Fig. the voltage across $$C$$ starts increasing when the $$d.c.$$ source is switched on. The rate of increase of voltage across $$C$$ at the instant just after the switch is closed (i.e., at $$t = {0^ + }$$), will be

In the circuit of Fig, the switch $$'S'$$ is closed at $$t=0$$ with $${i_L}\left( 0 \right) = 0$$ and $${V_C}\left( 0 \right) = 0.$$ In the steady state, $${V_C}$$ equals

The time constant of the network shown in Fig. is