5K10.65 - Earth Inductor - Jumping Rope

Code Number:
Demo Title:
Earth Inductor - Jumping Rope
Faraday's Law
Area of Study:
Electricity and Magnetism
50 ft extension cord with banana plug ends, Galvanometer, Oscilloscope.

Attach the loop at one end of the extension cord to the hook on the wall in the lecture rooms.  Stand in an east-west direction and spin one leg of the cord like a jump rope.  In our conditions we use the galvanometer to show about a 3 mv AC voltage.

Although the oscilloscope is more sensitive and should give a nice sine wave when doing this experiment, the cord acting as an antennae, picks up too much electromagnetic radiation from the machine room located below the lecture rooms.

  • Jarier Wannous, Peter Horvath, "Precise Measurements Using a Smartphone's Magnetometer - Measuring Magnetic Fields and Permeability", TPT, Vol. 61, #1, Jan. 2023, p. 36.
  • Roland Berger and Markus Schmitt, "Estimating the Earth's Magnetic Field Strength with an Extension Cord", TPT, Vol. 41, # 5, May 2003, p. 295.
  • Stanislaw Bednarek, "Showing Forces in the Terrestrial Magnetic Field", TPT, Vol. 37, # 6, Sept. 1999, p. 383.
  • Daniel L. Timmons,  "Finding Magnetic North the Hard Way",  TPT, Vol. 26, # 5, p. 276, May 1988.
  • Herbert H. Gottlieb, "Earth Inductor", TPT, Vol. 5, # 2, Feb. 1967, p. 86.
  • B- 210: "Jump Rope",  DICK and RAE Physics Demo Notebook.
  • Borislaw Bilash II, David Maiullo, "Tapping into the Earth's Magnetic Field", A Demo a Day: A Year of Physics Demonstrations, p. 306.
  • Jearl Walker, "5.47, Solar Eruptions and Power Outages", The Flying Circus of Physics Ed. 2, p. 239.

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