# Q & A: induction heating

Q:
i have neodymium magnets of 300 farenait that are inside a cooper pipe that is open on top. The motor run at 3400 rpm creating heat up to 300f do the magnets get demagnetized. watch video se i am talking about. http://www.youtube.com/watch?v=NivItikx0AU&feature=relmfu please reply if this works or not. thanks e.alexiou
- EFTHYMIOS ALEXIOU (age 52)
NEWTON
A:
I'm puzzled about what the point of this device is. Almost 2kW of electrical power is drawn by that motor. It spins some magnets near  a copper coil which is heated by the induction currents. That's a weird way to convert electrical power to heat, a task that any ordinary stove coil performs in a much simpler way.

Yes, as things get hot enough the magnets might lose a little magnetism, some of it irreversibly. You could directly measure that. As the copper heats up it gets less conductive, which reduces the eddy-current heating in it. That reduction of eddy currents must be the main factor giving the reduced power draw as things get hotter.

Mike W.

(published on 02/29/2012)

## Follow-Up #1: power through motor

Q:
Thank you for the answer . by the way the motor on video doesn't use 2kw it starts with 120v x 12.30amp = 1476 watts and it goes down to 9amp something. Appreciate again for your reply thanks again. E.Alexiou
- EFTHYMIOS ALEXIOU (age 52)
NEWTON
A:
We've corrected the power figure. Thanks,
Mike W.

(published on 03/02/2012)