A LEGO Watt Balance: a Simple Model of an Apparatus to Determine the SI Unit of Kilogram Using the Fundamental Planck’s Constant

Presenter(s)

Landon Boone, Lillian Gensolin

Abstract or Description

In 2019, the International System of Units’ unit of mass, the kilogram, was redefined based on the fixed value of the fundamental Planck’s constant, therefore eliminating the need for the International Prototype of Kilogram, the

platinum-iridium cylinder that was forged in 1879. The Kibble Balance, an apparatus that allows to realize the kilogram based on the Planck’s constant has been constructed at the National Institute of Standards and Technology (NIST). It is built on the idea of Bryan Kibble to balance the weight of the object by the electromagnetic force generated by the current-carrying coil immersed in a magnetic field. In 2015, a simple LEGO model of the Kibble Balance machine was constructed by NIST scientists [1]. The LEGO model does not utilize the Planck constant in the same way that the actual machine does, but rather serves as a demonstration of the ideas the actual machine is based on. The University of Tennessee at Chattanooga’s Society of Physics Students

(UTC-SPS) chapter constructed, calibrated, and put to action a LEGO-based model of the Kibble Watt balance. The project was funded by a SPS National research grant. Overall, the construction of the project allowed us as a chapter to improve our experimental skills and generate interest in both our SPS chapter and the Physics Program.

Mentor

Tatiana Allen