Temperature-sensitive resistive devices: Which component is deliberately designed so its resistance varies strongly with temperature?

Introduction / Context:
Sensors that translate physical variables into electrical signals are essential in control and measurement. For temperature, designers often use components whose resistance changes predictably with temperature to build simple, accurate measurement circuits.

Given Data / Assumptions:

• We are considering resistive components commonly found in basic circuits.
• Goal is to identify the one engineered for temperature dependence as its primary function.
• Both negative and positive temperature coefficients may exist.

Concept / Approach:
Thermistors are semiconductor resistors with a large temperature coefficient of resistance. NTC thermistors decrease resistance as temperature rises, while PTC types increase resistance. Their strong sensitivity enables compact thermometry and protection functions.

Step-by-Step Solution:
Define thermistor: a resistor optimized for temperature sensitivity.Contrast with potentiometer: a three-terminal adjustable divider for setting voltage; not inherently temperature sensitive by design.Contrast with rheostat: a two-terminal variable resistor for current control; again, not intended as a temperature sensor.Contrast with photoconductive cell: resistance varies with light intensity, not temperature.Therefore choose thermistor.

Verification / Alternative check:
Datasheets specify beta constants or temperature coefficients for thermistors, confirming their role in temperature measurement and inrush current limiting.

Why Other Options Are Wrong:
Potentiometer: manual adjustment; temperature dependence is an error term, not the feature.Rheostat: variable resistor for power control, not temperature sensing.Photoconductive cell: light-dependent resistor; senses illumination, not heat.

Common Pitfalls:
Assuming all resistors vary with temperature significantly; standard resistors aim for low temperature coefficient.Confusing thermistor behavior with RTDs; RTDs use metals with small, linear coefficients, while thermistors are semiconductors with larger, nonlinear response.

Final Answer:
Thermistor