Electromagnet Coil, Iron Cores, Variac, Pulse Switch, and Rings
Electromagnet Coil, Iron Cores, Variac, Pulse Switch, and Rings
Electromagnet Coil, Iron Cores, Variac, Pulse Switch, and Rings
EM Railgun

 

Code Number: 5K20.30

Demo Title: Lenz's Law - Jumping Rings

Condition: Excellent

Principle: Induction

Area of Study: Electricity & Magnetism

Equipment: 

Electromagnet Coil, Iron Cores, Variac, Pulse Switch, and Rings (Assorted).

Procedure:

Connect the electromagnet coil to a Variac.  Insert the iron core and place a ring over the core.  As you turn up the Variac the ring will appear to float.  Use a split ring or non-ferromagnetic ring and observe no effect.  Unplug the coil from the Variac and plug it into the pulse switch.  This allows you to input 110 volts AC instantaneously.  Place a ring over the core and hit the switch and the ring will jump about 20 feet into the air.

References:

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  • Andrew Duffy, "A Pictrorial Approach to Lenz's Law", TPT, Vol. 56, #4, Apr. 2018, p. 224.
  • Rondo N. Jeffery and Farhang Amiri, "Thomson’s Jumping Ring Over a Long Coil", TPT, Vol. 56, #3, Mar. 2018, p. 176.
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  • Carl S. Schneider and John P. Ertel, "A Classroom Jumping Ring", AJP, Vol. 66, #8, Aug. 1998, p. 686.
  • Benjamins S. Perkalskis and J. Reuben Freeman, "Extending Elihu Thomson's Demonstration and Lenz's Law", AJP, 65, #10, Oct. 1997, p. 1022.
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  • Freier and Anderson, "Em-12", A Demonstration Handbook for Physics.
  • B-260: Ring - Jumping and Heating", DICK and RAE Physics Demo Notebook.
  • "B-270: Attraction of Levitating Rings", DICK and RAE Physics Demo Notebook.
  • "B-265: Variable Levitation of Rings", DICK and RAE Physics Demo Notebook.
  • "5,000-MPH Bullets That Don't Need Gunpowder", Popular Mechanics, Feb. 2016, p. 66.
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  • Brian Jones and Matt Fackelman, "Ring Shooter", Don't Forget the Duct Tape, p. 125 - 128.
Video Credit: Jonathan M. Sullivan-Wood.
5K20.30 - Lenz's Law - Jumping Rings