5G20.70 - Electromagnet

Code Number:
Demo Title:
Area of Study:
Electricity & Magnetism
Small Electromagnet, 3 V battery system, 15 kilograms of weight.

Hang the electromagnet on a crossbar and energize the magnet.  Stick the face plate on the magnet and hang the weights from the hook on the face plate.  Disconnect the batteries from the magnet and watch the weights fall.

NOTE:  This magnet is rated at about 75 kg at 3 volts when operated properly, however we have several pieces of cellophane tape covering the face plate.

This is because without the cellophane tape the magnetized core still has significant lifting power and the magnet will not come apart easily.  With the cellophane tape in place we decrease the amount of weight that the magnet can hold but decrease the magnetic core problem.

The other way to do this is to replace the two hooks on the magnet with the rings and rope assembly.  This is so that several young children can pull on each section of the magnet at a time.  Should they proceed in pulling the magnet apart the chain will only allow the two halves to come 4" apart.

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  • Caroline Delbert, "How Do You Build the World's Largest Magnet?  It's Complicated", Popular Mechanics, November / December 2021, p. 32.

Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.