5K10.30 - Induced Currents using Two Coils

Code Number:
Demo Title:
Induced Currents using Two Coils
Induced Currents due to Changing Currents
Area of Study:
Electricity & Magnetism
6 or 12 Volt Batteries, Lecture Table Galvanometer, Key Switch, Coils (2) #'s 1 & 2 or 3 & 4 are Matched Sets, and Iron Cores. Small copper coil (3 inch diameter), LED's of different colors mounted on small copper coils.

Video Credit: Jonathan M. Sullivan-Wood

Connect the battery, one of the coils, and the key switch in series. Connect the galvanometer to the other coil. Place the coils side by side.  Depress the key switch and observe the deflection of the galvanometer. The deflection may be increased by inserting the iron core for greater classroom visibility. Note that as the switch is held down the galvanometer needle will return to zero as it is the changing of the fluxes that give the deflection. Choose your iron cores so that when both are inserted you get a full scale deflection on the galvanometer. DO NOT PEG OUT THE GALVANOMETER.

Smaller sets of nested coils and iron cores for mutual induction demonstrations are also available. 

The small 3 inch diameter coil is used with the small LED's that have been mounted on small copper coils.  Bring the coil near or over the LED's and observe the LED's light up.  

  • J. A. McNeil, "The Metal Detector and Faraday's Law", TPT, Vol. 42, # 6, Sept. 2004,  p. 369.
  • H. Richard Crane,  "Smart Ignition Systems on Modern Cars",  TPT, Vol. 24, # 7, p. 438, October 1986.
  • Ek - 4, 7:  Freier and Anderson,  A Demonstration Handbook for Physics.
  • B-220:  "Solenoids-Primary & Secondary",  DICK and RAE Physics Demo Notebook.
  • B-350:  "Iron Wire Core Increases Field",  DICK and RAE Physics Demo Notebook.
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  • Ron Hipschman, "Son of Transformer", Exploratorium Cookbook III, p. 152.1 - 152.3.
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  • W. Bolton, "Mutual Inductance", Book 4 - Electricity, Physics Experiments and Projects, 1968, p. 53.
  • C.J. Overbeck, R. R. Palmer, R. J. Stephenson, Marsh W. White, "Electromagnetic Induction", Cenco Selective Experiments in Physics, 1942, p.1-4.

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