5H25.25 - Magnetic Suction

Code Number:
Demo Title:
Magnetic Suction
Forces & Fields In and Around Coils
Area of Study:
Electricity & Magnetism
0 to 20 VDC Power Supply and Solenoid with Iron Core.

Hook the power supply to the solenoid and insert the iron core half way. When the power supply is switched on at maximum voltage the iron core will be sucked into the solenoid and center itself.

The puzzle to this problem is: Where does the energy to pull the core into the coil come from? Ultimately this will be from the battery or the power supply, but it is not obvious. The current drops as the core is being drawn into the coil because of Lenz's law. But since it drops, the ohmic losses do too and the difference is the power that does the work to pull the core in.

  • David Kutliroff, "97, An A.C. - D.C. Current Meter", 101 Classroom Demonstrations and Experiment For Teaching Physics, p. 213.
  • Ron Hipschman,  "Magnetic Suction",  Exploratorium Cookbook III,  p. 147.1 - 147.3.
  • "Magnetic Suction",  The Exploratorium Science Snackbook,  65.1 - 65.2.
  • Rudolf F. Graf, "The Magic Driver", Safe and Simple Electrical Experiments, p. 103.

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