5K20.31 "Elihu Thomson"-type Jumping Ring

PURPOSE: To demonstrate Lenz' Law

DESCRIPTION: Connect the coil of the Jumping Ring demonstration (see 5K20.30) to an AC ammeter, to show how the current increases when the ring is forced down on the core.

SETUP TIME: Medium

COMPONENT LIST:

    


  1.  AC driven coil				?????


  2.  Core with Al Ring				?????

SUGGESTIONS: This is an example of the reaction of the secondary upon the primary. Alternatively, one could view the ring as constituting a shorting turn which decreases the impedance of the coil-and -core combination.

REFERENCES: 2122 4.965 ; PIRA 5K20.31

OTHER NOTES: The ring also constitutes a single-turn transformer secondary which draws a heavy current from the driving coil when it's forced down and held (you can feel the ring get painfully hot).