Circuit Diagram Variable Resistor. Connect the circuit as shown in the diagram. As the name suggests the variable resistor is a passive three terminal device that can adjust its resistance via third terminal located between two terminals so that the obstruction to the flow of current goes up and down.
By varying the resistance rce. Variable resistors are those whose resistance values can be varied or changed at any time. Variable resistor circuit.
The second part of the circuit is transistor section where transistor acts as a switch for led d1.
Also by replacing thermistor with a variable resistor we can study its equivalent effect in the circuit as per the below circuit diagrams. The diode must be protected with a suitable protective resistor between 100 omega and 500. The collector emitter resistance rceis controlled by the base current ib. The circuit can also be controlled with pulse or digital input from any other source.