Faraday's Electromagnetic Induction

Author(s): Aldo Cos & Tom Schuster
Demonstration Equipment - Teacher's Guide
SED 695B; Fall 2005

Principles illustrated:

Electromagnetic Induction


Standards addressed:

Physics 5f:
Students know magnetic materials and electric currents (moving electric charges) are sources of magnetic fields and are subject to forces arising from the magnetic fields of other sources.


Explanation of principles involved
  • Primary Secondary Coil Induction Set (Science First item #10-140)
  • 4.5V Battery
  • Galvonometer
  • Switch
  • Aligator Clips (4)
  • Paper Clips
Students may wonder how transformers and generators work. Here is described a potential lab or demonstration of Faraday's principle of electromagnetic induction.Since the copper coils contain a changing electric charge, an object placed within the electric field will become charged (magnetized). When the rod is pushed in and out of the coils, the magnetic field around the coils is changed. This in turn makes the electrons (current) in the coil move. This can be observed by the alternating (+) and (-) movements on the galvanometer. Alternatively, or additionally, the apparatus can be rearranged so that an electrical current generated from a battery is passed through the coil. The rod becomes magnatized and can be used to pick up small metal objects, like paper clips.


  • Gather materials
  • Connect the primary (larger) coil to the galvanometer using the aligator clips
  • Move the rod in and out of the coil and observe the galvanometer move in the direction of the motion
  • Reconfigure the wires and clips so that the battery completes the circuit with the large coil.
  • Demonstrate that the rod, when placed within the coil, is now magnatized and will pick up paper clips, tacs, and staples.
  • Use the same arrangement with the battery, this time using the smaller diameter coil. Note that, with its greater number of windings, the smaller diameter coil will produce a stronger magnatism than the larger coil. The rod in the smaller coil will pick up more clips.
  • Record results in a data table
  • Have students answer questions
  • Brainstorm the "realworld" applications of electromagnetic induction


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