MEASURING THE THERMAL EXPANSION COEFFICIENT OF AIR

Abstract

In this article, we build a low-cost version of Galileo’s thermoscope to measure the coefficient of thermal expansion of air. Historically, the thermoscope was the first instrument capable of measuring temperature variation. Its low-cost version was built with a ping pong ball attached to one end of a plastic tube and the other end of the tube was inserted into a plastic cover containing water with red food coloring. We use the palm of the hand to heat the air inside the of ping pong ball, when heated, the air expands, increasing its volume. The temperature variation was measured using a temperature sensor, the acquisition of these data was obtained through the Arduino platform and the volume variation was measured by video analysis, using the Tracker program. With the measurements of these two quantities, we can determine the coefficient of thermal expansion of the air that was C-1. The percentage difference between the experimental value and the theoretical value was approximately. The experiment was performed in a closed system as the relative change in volume per unit change in temperature at constant pressure. This practice provides students, both in the second year of high school and in the subject of thermodynamics in higher education, the opportunity to prove the theory that is presented in the classroom.