Why you use capacitor before connecting transtitor?

Answer 1

Before connecting to the transistor we use a capacitor because

for the transistor to amplify we should first apply DC biasing so that we can set an operating point to it
so once the transistor is biased DC currents flow in the whole circuitry

All the AC signal source are shorts to the DC currents so we employ capacitor for two reasons

1.As capacitor blocks DC and allows AC it is connected for not moving the DC operating point of the transistor and making it fixed since if any small DC part arises in the signal it leads to the change of operating point and our amplification procees gets affected

2.To block the already present DC currents in the circuitry for not getting away and making it fixed