Component classification: A thermistor belongs to which category of electrical component based on its primary function?

Introduction / Context:
Thermistors are ubiquitous in temperature sensing, compensation, and protection (inrush limiting). Knowing their fundamental category and behavior is key to selecting and modeling them in circuits and control systems.

Given Data / Assumptions:

• A thermistor exhibits resistance that varies predictably with temperature.
• NTC (negative temperature coefficient) and PTC (positive temperature coefficient) types exist.
• The question asks for the broad component category, not a specific application.

Concept / Approach:

A thermistor is a temperature-dependent resistor. Its resistance changes significantly with temperature, enabling temperature measurement or compensation. As a passive component, it does not supply energy like a battery or power supply, nor does it perform the discrete on/off function of a switch (though PTC thermistors can behave as resettable protectors).

Step-by-Step Solution:

Verification / Alternative check:

Datasheets specify R25 (resistance at 25 °C) and Beta or alpha parameters, all of which are resistor-centric characteristics, confirming classification.

Why Other Options Are Wrong:

Switch indicates discrete on/off control, which is not the thermistor’s primary role. Battery and power supply are energy sources. Capacitor stores electric field energy; a thermistor does not.

Common Pitfalls:

Assuming PTC resettable protectors are 'switches'; they are still resistors whose resistance increases sharply with temperature, creating a protective effect rather than a true mechanical or semiconductor switch action.

Final Answer:

resistor