May I get the explanation of Kirchoffs law used in the working of transistor as a switch?

The Bipolar Junction Transistor can be used as a switch. This is required when the typical digital output does not provide sufficient current drive for high current devices like lamps, solenoids or motors. The transistor current gain provides the order of magnitude increase in collector current.We can use kirchoffs voltage law and current law around the circuiit.Because a transistor's collector current is proportionally limited by its base current, it can be used as a sort of current-controlled switch. A relatively small flow of electrons sent through the base of the transistor has the ability to exert control over a much larger flow of electrons through the collector.