Question

How does the heat affect resistance?

Answer 1

Hint: As temperature is the unit to measure heat, we can discuss our answer in terms of temperature. The electric resistance keeps on changing with the change in temperature but change is not well defined here, sometimes it increases and in some cases it decreases with the increase in temperature.

Complete answer:
Resistance is said to be the obstruction offered by the material to the flow of charge or current. It is measured in ohm. Based on the electric resistance, materials are categorized broadly into three categories as follows.
Metal
Alloy
Semiconductor.
Now, let’s discuss the effect of change in temperature on the resistance of the above material.
For metal, the resistance increases linearly with the increase in temperature. As the temperature increases, ions in the material start vibrating and colliding and hence the resistance increases.
In alloy, resistance increases with the increase in temperature but the rate of increase is slower than that of metal and for some alloy there is no change in resistance over the considerable change in temperature.
The resistance of a semiconductor decreases with the increase in temperature. As the temperature increases, some electrons of the semiconductor acquire energy and become free for conduction. Hence, resistance decreases with increase in temperature.

Note:
Resistance is not only dependent on heat or temperature of a material but it also depends upon the length and cross sectional area along with the resistivity, resistivity is the fundamental property of a material which does not change.