Experiment Readout
Ring: Solid ring
Power source: DC
Ring height: ready
Result: waiting
This interactive 3D physics simulation demonstrates the jumping ring experiment, also called the Thomson ring experiment. A conducting ring is placed above a coil with an iron core. When the current in the coil changes, the changing magnetic flux induces current in the ring and creates magnetic repulsion.
1. Coil and iron core: create a strong magnetic field through the ring.
2. Conducting ring: carries induced current when magnetic flux changes.
3. Power source: compares AC and DC behavior in electromagnetic induction.
4. Liquid nitrogen beaker: represents cooling the ring to reduce resistance.
The minus sign in Faraday's law represents Lenz's law. The induced current produces a magnetic field that opposes the change in magnetic flux. In the jumping ring experiment, this opposition appears as an upward magnetic force on the ring. A closed conducting ring can jump because current can circulate. A slit ring has no complete path for large induced current, so it barely jumps.
AC changes continuously, so the magnetic flux through the ring keeps changing. This produces a stronger and more sustained induced current. DC produces a brief induction effect mainly when the switch is turned on or off; after the current becomes steady, the magnetic flux no longer changes and induction stops.
Cooling the ring lowers its electrical resistance. Lower resistance allows a larger induced current for the same changing magnetic flux. As a result, the magnetic repulsion is stronger and the ring can jump higher.
In a real jumping ring demonstration, the magnetic field is invisible. In this simulation, the moving ring, coil, power supply, and readouts help students connect the visible jump to induced emf, magnetic flux, and Lenz's law.