A hydrogen atom falls from $n$th higher energy orbit to first energy orbit $(n=1)$. The energy released is equal to 12.75 eV . The $n$th orbit is

The decrease in each day in the uranium mass of the material in a uranium reactor operating at a power of 12 MW is (Energy released in one ${ }_{92} \mathrm{U}^{235}$ fission is about 200 MeV )

When a signal is applied to the input of a transistor, it was found that output signal is phase-shifted by $180^{\circ}$. The transistor configuration is

The voltage $V_0$ in the network shown is