Magnetic pendulum apparatus for analog demonstration of first-order and second-order phase transitions and tricritical points

Abstract

A simple apparatus is described in which the deflection of a pendulum with an electromagnet mounted at its tip is the analog of the magnitude of the order parameter in a phase transition. Its deflection is governed by the current through this electromagnet and currents through fixed electromagnets just below it. By suitable variation of these currents, the pendulum can be made to undergo gradual (second‐order transition analog) or sudden (first‐order transition analog) displacements from the vertical, as well as the intermediate situation corresponding to a tricritical point. Results for critical and tricritical exponents obtained with this apparatus are presented.