Which statement describes a temperature-sensing element based on resistance?

• A. Its resistance changes with temperature.
• B. It emits light when heated.
• C. It generates voltage with magnetic field.
• D. It uses capacitance.

Answer: (A)

A temperature-sensing element that relies on resistance works because the electrical resistance of a material changes with temperature. This is the defining behavior of resistive temperature sensors: the sensor is a resistor whose value shifts as the surrounding temperature changes.

In practice, metals like platinum are used in resistance temperature detectors (RTDs). Their resistance increases roughly linearly with temperature, so you measure the resistance and convert it to temperature using a calibration curve. To get accurate readings, the measurement often uses a four-wire or bridge configuration to cancel lead resistance and minimize error. Thermistors, which are semiconductor-based, also rely on resistance changing with temperature, but their response is typically nonlinear (NTC means resistance drops as temperature rises, PTC means resistance rises).

The other options describe different phenomena—emitting light when heated (not a resistance-based method), generating voltage with a magnetic field (Hall effect or magnetoresistive sensing), or changing capacitance (capacitive sensing). None of these describe a resistance-based temperature element, which is all about how resistance varies with temperature.