A transistor is operated in common emitter configuration at $V_{\mathrm{C}}=2 \mathrm{V}$ such that a change in the base current from $100\mu \mathrm{A}$ to $300 \mu \mathrm{A}$ produces a change in the collector current from $10 \mathrm{mA}$ to $20 \mathrm{mA}$ . The current gain is

Find the current flowing through the $1 \mathrm{k\Omega }$ resistor shown in the figure. 

In the circuit shown below, the voltage across the $2 \mathrm{k\Omega }$ resistor is 

The resistance of a germanium junction diode whose $V-I$ is shown in the figure is $\left(V_k=0.3 \mathrm{V}\right)$

The circuit shown in the figure contains two diodes each with a forward resistance of $50 \mathrm{\Omega }$ and with infinite reverse resistance. If the battery voltage is $6 \mathrm{V}$, find the current through the $100 \mathrm{\Omega }$ resistance.

The barrier potential of a silicon diode is $0.7 \mathrm{V}$ at $25°\mathrm{C}$. Find the barrier potential at $-20°\mathrm{C}$ and at $110°\mathrm{C}$.

Two identical $P$ - $N$ junction may be connected in series with a battery in three ways (figure). The potential drops across the two $P$ -$N$ junction are equal in-