Magnetic field in induction furnace

[Peethol]

Hi

I'm trying to make my own small induction furnace. I've made a small coil, the same shape as a solenoid. I'm using the electronics of a small induction stove so that is all in working order.

[PLAIN]http://upload.wikimedia.org/wikipedia/commons/archive/4/45/20091002222929!Solenoid-1.png

For testing purposes, I'm using a round magnetic bar inserted into the middle of the coil. The coil is about 30cm long and the bar is about 1 meter long. The problem is, that when I stick the bar completely through the coil, so that the coil is in the middle of the bar, the bar doesn't get heated. But as soon as I stick the bar only halfway through the coil it gets very hot.

Can anyone explain to me why this is happening?

Thanks in advance :-)

 

[nikhil khatri]

the reason can be that ,when u completely fill the coil with the bar there is no change in magnetic flux in the coil &so no current is induced in the coil & thus coil is not heat up but when u stick the magnet in half of the coil flux in the coil varies & current is induced resulting in heating of coil.