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Encyclopedia of Electrical Engineering
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HOME TABLE OF CONTENTS
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Encyclopedia of Electrical Engineering
HOME TABLE OF CONTENTS PROJECTS TECHNOLOGY
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Temperature Effect

Temperature has a significant effect on the resistance of conductors, semiconductors, and insulators.

Effect on Conductors

Conductors have a generous number of free electrons, and any introduction of thermal energy will have little impact on the total number of free carriers. In fact, the thermal energy only increases the intensity of the random motion of the particles within the material and makes it increasingly difficult for a general drift of electrons in any one direction to be established. The result is that for good conductors, an increase in temperature results in an increase in the resistance level. Consequently, conductors have a positive temperature coefficient. The plot in Fig. no.1 has a positive temperature coefficient.
Fig.no.1: Effect of temperature on the resistance of copper.

Effect on Semiconductors

In semiconductors, an increase in temperature imparts a measure of thermal energy to the system that results in an increase in the number of free carriers in the material for conduction. The result is that for semiconductor materials, an increase in temperature results in a decrease in the resistance level. Consequently, semiconductors have negative temperature coefficients.

Effect on Insulators

As with semiconductors, an increase in temperature results in a decrease in the resistance of an insulator. The result is a negative temperature coefficient.