School of Physics Lecture Demonstration Manual

Eb-5 The Jumping Ring

Published: Tuesday 14 March 2006 - Updated: Tuesday 29 March 2011

Aim

To demonstrate the repulsion between a conductor and a circuit carrying an alternating current.

Apparatus

Diagrams

Click on pictures to enlarge.

Jumping Rings Pic

Jumping Ring Diagram

Videos

Jumping Rings

Description

The electromagnet is connected to the variac with the ring/s placed over the central core. As the variac voltage is increased the solid ring will "levitate" due to the interaction between the induced and primary currents. The incomplete ring will not be affected. The part the resistance plays in the phase delay between the currents may be demonstrated by cooling the ring in liquid nitrogen and repeating the above experiment, though of course the size of the currents is also affected.

 Caution :  When energized, the apparatus becomes a strong electromagnet. The top bar is attracted to the C-yoke with great force. Be sure fingers and hands are clear of the apparatus. Do NOT energize the apparatus until it is clear and a safety check has been made, as a servere pinch hazard exists.

Safety notes

Electrical safety 

Maintenance 

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