Draw the forward and reverse characteristics of a semiconductor diode.

How $p-n-p$ and $n-p-n$ transistors are represented symbolically?

What is the difference between an $n$ -type and a $p$ -type semiconductor ?

How does the depletion region of a $p-n$ junction diode get affected under reverse bias?

The output of an unregulated dc power supply needs to be regulated. Name the device that can be used for this purpose and draw the relevant circuit diagram.

Two semiconductor materials $X$ and $\underset{¯}{Y}$ shown in Fig. $21.80$ are made by doping germanium crystal with indium and arsenic respectively. The two are joined end to end and connected to a battery as shown.

Sketch a $\mathrm{V}$-$\mathrm{I}$ graph for this arrangement. 

What do the terms ‘depletion region’ and ‘barrier potential' mean for a $p-n$ junction?

In a transistor, doping level in base is increased slightly. How will it affect

$\left(\mathrm{ii}\right)$ base current.