PURPOSE: To illustrate materials with both positive and negative temperature coefficients of resistivity.

DESCRIPTION: Approiximately equal copper and carbon resistors are mounted on plastic mount which can be inserted into liquid nitrogen. When cooled from room temperature to the temperature of liquid nitrogen the resistance of the copper resistor decreases from 15.3 ohms to 2.0 ohms (left and center left below), while the resistance of the carbon resistor increases from 16.6 to 20.7 ohms (center right and right below).

SUGGESTIONS:

REFERENCES: (PIRA unknown.)

EQUIPMENT: Mounted copper and carbon resistors, liquid nitrogen, and digital meter.

SETUP TIME: 10 min.