An n-p-n transistor can be considered to be equivalent to two diodes connected. The correct figure out of the following is

Find the magnitude of current in the given circuit.

In common emitter transistor amplifier, load resistance is $6.5 \mathrm{k} \Omega$ and an input resistance is $1.3 \mathrm{k} \Omega$. If the current gain is 78 , the voltage gain is

The potential barrier in p-n junction diode is due to