Which of the following is a nonlinear component used in switching or amplification?

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

Answer: (A)

The main idea is that a nonlinear, active device can provide gain and switch states, unlike passive linear elements. The transistor fits this role because its base-emitter junction behaves like a diode, giving a nonlinear current–voltage relationship. A small change at the input controls a much larger current in the collector, providing amplification. In switching modes, driving the transistor into saturation or cutoff toggles the output quickly, acting like a fast on/off switch. In contrast, a resistor is linear and obeys Ohm’s law, with current proportional to voltage. A capacitor stores charge and responds to changes in voltage, while an inductor stores energy and responds to changes in current; neither inherently provides amplification or fast switching. So the transistor is the nonlinear component used for switching or amplification.