How P-N-P and N-P-N transistor are represented symbollically?

How does a P-N junction break down?

P-N junction is:

How the common emitter n-p-n transistor is used as a switch? Explain with the help of a circuit diagram.

If the emitter and base of n-p-n transistor have same doping concentration, explain, how will the collector and base currents be affected.

In a p-n-p transistor circuit, the collector current is 10mA , If 90% of the electrons emitted reach the collector , what is base current ?

Discuss the working of p-n-p transistor as an amplifier in common emitter mode.