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Code Number: 5K10.51
Demo Title: Induced Currents using Two Coils - Audio Transformer
Condition: Excellent
Principle: Induced Currents due to Changing Currents
Area of Study: Electricity & Magnetism
Equipment:
Portable Radio/Tape Player, 7, 15, 21, and 30 Turn Coils, Speaker/Amplifier, Iron Cores or Closed Loop of Iron (Transformer U Yoke).
Procedure:
Plug one of the 15 turn coils into the tape player and play a tape. Plug the other 15 turn coil into the speaker / amplifier and turn this on. As you bring the two coils together the sound will intensify as the distance is decreased. An iron core will greatly increase this effect. Coil turn ratios may be explored using the 7 and 21 turn coils.
A cool spoof is to put the 30 turn coils on each side of a "volunteer's" head and listen to the "song stuck in their head". This shows that radio waves are in no way blocked or attenuated by the human body.
References:
- Don Rathjen, "Modulated Coil", TPT, Vol. 36, #7, Oct. 1998, p. 416.
- Don Rathjen and Paul Doherty, "Modulated Coil", Square Wheels, 2002, p. 49.
- Borislaw Bilash II and David Maiullo, "Transform the Volume", A Demo a Day: A Year of Physics Demonstrations, p. 311.
- Marsha Hobbs, "Radio Transformer", PIRA News, Vol. 6, #3, Feb. 1993.