How transistor can be used an amplifier?

Why transistor can't be used as a rectifier?

How transistor can be used as an oscillator.

Explain, how a transistor can be used as a switch with the help of a circuit diagram.

In a transistor, the base current is changed by 20muA . This results in a change of 0.02V in base emitter voltage and a change of 2mA in the collector current. .If the transistor is used as an amplifier with load resistance of 5KΩ .Find its voltage gain.

Draw the circuit diagram of a common emitter n-p-n transistor as an amplifier. Would you prefer to use a transistor as a common base or a common emitter amplifer and why?

How junction Diode can be used as a full wave rectifier.

The input resistance of a silicon transistor is 100 Ω. Base current is changed by 40μA which results in a change in collector current by 2 mA. This transistor is used as a common emitter amplifier with a load resistance of 4K Ω. Find the voltage gain of the amplifier.