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Step 16 Connect the positive terminal of the buzzer to the emitter terminal of the third transistor.
Step 17 Connect the negative terminal of the buzzer to the negative rail of the breadboard.
Connect a wire here
Connect a wire here
Circuit Operation
When the water level reaches a certain point, it completes the circuit by connecting to the base of
the NPN transistor. This activates the transistor, allowing current to flow from the collector to the
emitter. As a result, the connected LED lights up and the buzzer sounds, indicating the water level
has been reached.
Concept
In this activity, an NPN transistor acts as an electronic switch. When the water level rises and
touches a sensor, it completes the circuit, sending a small current to the base of the transistor. This
triggers the transistor to allow a larger current to flow between the collector and emitter, which
Electronics with Breadboard-Based Kit 47
