Which of these components can be used as an electronic switch?

• A. Capacitor
• B. Diode
• C. Transistor
• D. Resistor

Answer: (C)

A transistor is a component that can function as an electronic switch due to its ability to control the flow of current between its terminals based on the input signal applied to its control terminal (the gate or base). When a small current is applied to the base of a bipolar junction transistor (BJT) or a suitable voltage is applied to the gate of a field-effect transistor (FET), it allows a significantly larger current to flow between its collector and emitter or drain and source, respectively. This property makes transistors ideal for switching applications, allowing them to turn on or off circuits, amplify signals, or act as digital logic gates in more complex digital circuits.

In contrast, capacitors are primarily used for storing electrical energy and filtering signals, diodes allow current to flow in one direction and can be used for rectification or signal demodulation but do not act as switches, and resistors are intended to limit current flow and are not capable of switching. Each of those components has a distinct role in electronic circuits, but it is the transistor that uniquely combines amplification and switching capabilities, making it essential in numerous applications within electronics.