Thermistors and material class: thermistors have a very high (negative or positive) temperature coefficient of resistivity. They belong to which class of solids?

Introduction / Context:
Thermistors are temperature-sensitive resistors widely used for precision measurement, compensation, and control. Their defining feature is a large temperature coefficient of resistance, typically negative (NTC) but sometimes positive (PTC). Correctly classifying their material type clarifies why their resistance changes so strongly with temperature.

Given Data / Assumptions:

• Thermistors show large dR/dT magnitudes.
• Common compositions include metal oxides sintered into beads or chips.
• Applications range from temperature sensing to inrush current limiting.

Concept / Approach:
Thermistors are made from semiconductor materials. In NTC thermistors, increasing temperature excites more charge carriers, reducing resistance sharply. In PTC thermistors (such as doped barium titanate), a phase transition or band structure effect increases resistance with temperature. These behaviors are characteristic of semiconducting solids, not good conductors or pure insulators.

Step-by-Step Solution:
Relate strong temperature dependence of resistivity to semiconductor physics (carrier concentration).Identify typical thermistor construction: metal oxide semiconductors like Mn, Ni, Co oxides.Conclude class: semiconductors.

Verification / Alternative check:
Device datasheets plot log(R) versus 1/T (Arrhenius-like), a hallmark of semiconductor conduction mechanisms.

Why Other Options Are Wrong:
Dielectrics/Insulators: Very high resistivity with relatively small temperature dependence in normal ranges.Conductors: Metals have positive but modest temperature coefficients, far smaller than thermistors’.Superconductors: Exhibit zero resistance below critical temperature, unrelated to thermistor behavior.

Common Pitfalls:
Assuming “resistor” implies metallic conductor; in thermistors, the dominant physics is semiconducting carrier behavior.

Final Answer:
Semiconductors