5K20.36 - Induction Heating - Boil Water

Code Number:
Demo Title:
Induction Heating - Boil Water
Area of Study:
Electricity & Magnetism
Electromagnet Coil, Iron Cores, Variac, Ring with groove, Water, Small Induction unit, nails ( with pliers to hold the nails) , digital thermometer.

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.

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