70. Temperature Coefficient of Resistance

The temperature coefficient of resistance can be investigated with a copper wire wound resistor and a carbon resistor. A small circuit with a battery, lightbulb and resistor is set up and then the resistor is put into a cup of liquid nitrogen. The change in light brightness indicates the sign of the temperature dependence. The temperature dependence of a semiconductor can be investigated by dipping a large green LED into liquid nitrogen and noting the color change.