The time variations of signals $A, B$ and $C$ are shown below. Choose the correct statement.

Which of the following figures correctly shows the phase relation between the input signal and the output signal of a common-emitter transistor amplifier?

The figure shows an intrinsic semiconductor $S$ connected in series with a variable resistor $R$ and a constant voltage source $V$. The value of $R$ can be adjusted to maintain a constant current in the ammeter $A$. Under what condition will the semiconductor $S$ get heated? Give reasons.

The amplifiers $X, Y$ and $Z$ are connected in series. If the voltage gains of $X, Y$ and $Z$ are $10, 20$ and $30$ respectively,and the input signal is $1 \, mV$ peak value,then what is the output signal voltage (peak value) $(i)$ if $DC$ supply voltage is $10 \, V$? $(ii)$ if $DC$ supply voltage is $5 \, V$?

Three amplifiers with voltage gains $10, 20$ and $30$ are connected in series. If the input signal has a peak value of $1 mV$, then the peak value of the output voltage is (in $\,V$)

The energy of a photon of sodium light $(\lambda = 589 \text{ nm})$ is equal to the band gap of a semiconductor. Find the minimum energy $E$ in $eV$ required to create an electron-hole pair.