Phase Shift and The Jumping Ring

Thumbnail Image
Luke, Ella
Bronkhorst-Ilavsky, Simon
Rantz, Lucas
Littmann, Nika
This experiment centered around and developed the model of the Thomson Jumping Ring. The purpose of this experiment was to move past the weak Lenz’s Law justification and provide another explanation for the jumping phenomena: the phase shift between driving and induced currents. By measuring the driving and induced currents for a range of frequencies, the phase shift was determined. The phase shift was compared to induced current and it was shown that induced current is directly proportional to sin of the phase shift, demonstrating that induced current increases at higher phase shifts. Larger induced currents lead to stronger force interactions with the solenoid’s magnetic field, which shows that the magnitude of the force acting on the ring is related to phase shift. The jump height of the ring and observations of its behaviour when it was allowed to levitate proved that the direction of the force acting on the ring is also importantly proportional to phase shift. At small phase shifts, the force acting on the ring oscillates between pushing it up and pulling it down, and as phase shift increases the force proportionately spends more time per oscillation pushing up. At very high frequencies, the force acts entirely to push the ring upwards. These two dependencies on phase shift, one for the magnitude of force and one for direction of the force, show that Lenz’s Law is not enough to describe the Thompson Jumping Ring phenomena, and that an analysis of the ring and solenoid current phase shift is required.
External DOI