Coefficient Of Linear Expansion

Coefficient of Linear Expansion

Navin J. Ramjassingh PHY 136

Objective: We will study the thermal expansion of a solid by measuring the coefficient of linear expansion of a metal rod.

Theory and Discussion: During heat transfer, the energy that is stored in the intermolecular bonds between atoms changes. When the stored energy increases, so does the length of the molecular bond. As a result, solids expand in response to heating and contract on cooling. This response to temperature change is expressed as its coefficient of thermal expansion. The linear thermal expansion coefficient relates the change in temperature to the change in a material’s linear dimensions. It is the frational change in the length of a bar per degree of temperature change. The fractional change in length which is a natural quantity to use is the difference in length of the micrometer measurements (initial minus the final) divided by the length of the metal rod used. This is equivalent to the expansion coefficient multiplied by the change in temperature of the metal rod used.

Similarly to the diagram above we proved the theory of the coefficient of thermal linear expansion. The micrometer form was referred to as the “dial gauge.” As well as the Thermometer was used along with the “thermistor” as shown in the diagram. The metal used was Steel with a standard expansion coefficient of 1.2 x 10-3 .

Summary: After boiling the water for approximately twenty minutes, we observed a change in temperature of the metal rod from 27.2°C to 100.6°C. With the change in temperature factor and the change length factor (initial – final), which were measured using a micrometer, we could then calculate the experimental coefficient of thermal linear expansion (1/°C). By comparing that to the standard value we came up with a percent error of 22.5%. But due to the comparison between the change in temperature and change in length, we can clearly conclude that the metal expanded by a difference of 0.41mm.