College of Liberal Arts & Sciences
5K20.36 - Induction Heating - Boil Water
Connect the electromagnet coil to a Variac. Insert the iron core. Use the hemostats to hold on to the copper ring that has the groove in it. Place 1 or 2 ml of water into this groove and place the ring over the electromagnet. Turn the Variac up to 40 and hold the ring down in the oscillating magnetic field (in other words, don't let the ring float). The water should start to boil with steam evolution in less that 30 seconds.
The small induction unit is very good for small scale demonstrations. Plug it in and insert a digital thermometer probe into the middle of the coil. Observe the temperature dramatically and quickly increase past 100 degrees C. You may also use a pliers to insert the nail with the thermocouple probe attached into the coil and observe the temperature increase of the nail. Note that you need to use the pliers as the nail will quickly heat to a temperature that will produce severe burns. The small blue LED light on the unit will go out if you have inserted the nail too far into the coil ( which signals coil overload). SPECIAL NOTE: Only plug this unit in just before you intend to use it, and unplug it just as soon as you are done doing the demonstration so that any chance of the unit overheating is reduced.
- Thomas B. Greenslade Jr., "Apparatus Named After Our Academic Ancestors, III", TPT, Vol. 52, # 6, Sept. 2014, p. 360.
- A. Gavrin, "Induction or Hysteresis: No Longer a Burning Issue", TPT, Vol. 39, # 6, p. 354, Sept. 2001.
- Baki Brahmia, George Horton, "Induction or Hysteresis: That Is the Cooktop Question", TPT, Vol. 39, # 2, p. 80, Feb. 2001.
- Thomas B. Greenslade, Jr., "Foucault's Disk (Photo)", AJP, Vol. 70, # 11, Nov. 2002, p. 1135.
- B-260, Dick and Rae Physics Demo Notebook, "Ring - Jumping and Heating".
- Harry Sawyers, "Cooking With Joule", Popular Mechanics, August 2010, p. 80.
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.