Define temperature coefficient of resistance. Explain whether it is positive or negative forconductor, semiconductors and insulators with rise in temperature

The temperature coefficient of resistance, often denoted by the Greek letter alpha (α), is a measure of how much the electrical resistance of a material changes per degree change in temperature. It is usually expressed in per degree Celsius (°C⁻¹) or per degree Kelvin (K⁻¹).

For conductors, the temperature coefficient of resistance is usually positive. This means that as the temperature increases, the resistance of the conductor also increases. This is because, at higher temperatures, the atoms of the conductor vibrate more rapidly, which increases the likelihood of collisions with the charge carriers (usually electrons), thereby increasing the resistance.

For semiconductors, the temperature coefficient of resistance is typically negative. This means that as the temperature increases, the resistance of the semiconductor decreases. This is because, at higher temperatures, more electrons are excited into the conduction band, thereby increasing the number of charge carriers and decreasing the resistance.

For insulators, the temperature coefficient of resistance can be either positive or negative, depending on the specific material. However, since insulators are typically used in conditions where they are not supposed to conduct electricity, changes in their resistance with temperature are usually not a significant concern.