Re: Does heat destroy a permenant or an electromangnet force.Ifso how much heat

The answer is both yes and no.  If you apply enough heat to raise the 
magnet above its Curie Temperature (you can look up the Curie Temperature 
for a substance in the CRC Handbook of Chemistry and Physics, among other 
places), then it will lose all of its spontaneous magnetization.  However, 
when you lower the temperature again the magnetization will return.  Short 
of changing the composition of the magnet, I know of no way to permanently 
destroy the magnetization of a permanent magnet.

I should add a qualification to this.  While the magnet will always have a 
magetization when it is cooler than its Curie Temperature, different parts 
of the magnet will have magnetization in different directions.  You can 
"scramble" the magnetization of a permanent magnet by heating it and 
applying a rapidly varying magnetic field.  Or by hitting it with a hammer.  
When magnets weaken over time, this is what is happening.