Step No.2 Connect a 9V Battery on the breadboard
Step No.3 Connect a NPN transistor on the breadboard with its 3 pins ( emitter base and collector) in 3 different holes on the breadboard
Step No.4 Connect the emitter to the ground (Negative Terminal)
Step No.5 Connect a LED and a resistor between collector and positive terminal of the battery . The LED won’t glow.
Step No.6 Connect a wire between base and collector. The LED starts glowing.
Step No.7 When the wire is disconnected, the LED stop glowing again.
Reasoning In a transistor, the collector current is proportional to the base current. The connection between base and collector allows the base current to flow. In the absence of that connection, base current is zero resulting in zero collector current. We are using NPN transistor here. PNP transistor can also be used. The distinction between two transistor is made by the number on them.
FSNS You only learn by doing it yourself From Scrap and Scratch