Which of the following is NOT a passive electrical component?

The story behind the answer

Transistor is the only active component listed: it can control and amplify signals and requires an external power source (bias) to operate. In contrast, resistors, capacitors, and inductors are passive—they cannot provide power gain. Resistors dissipate energy as heat, capacitors store energy in electric fields, and inductors store energy in magnetic fields; none can amplify a signal.

Context: The transistor, invented in 1947, is the foundation of modern electronics, enabling switching and amplification in everything from radios to smartphones. Memory tip: think “RLC” (Resistor, Inductor, Capacitor) as the classic passive trio; the odd one out—“T” for Transistor—is active.