When alternating current flows in a ferromagnetic material it gets heated up by the eddy currents. It cans be easily compared with a transformer. In the transformer by electromagnetic principle electrical energy transferred from primary to secondary of transformer it is used when a load is connected in secondary side. Here we say that in induction heating the energy transferred from primary is directly utilized in the secondary.
figure Solid metallic cylinder heated by induction heating
Consider a long solid metallic cylinder which is heated by a long helical coil wound over it in account of analyses the factors the affecting induction heating let number or turns over the metal piece be N length of coil be I meters and the resistivity of the material be e r. M.
When an alternating current I1 of frequency f flows in the coil an alternating flux ? is set up. The direction of this flux is along the axis of the coil. An induced emf product in the coil which is responsible to flow the eddy current in metal piece. The power loss of eddy current in the metal piece produces heat. Here we can assume that if material to be heated acting as one turn secondary then the ampere turns of primary should be equal to that of secondary .
I1 N1 = I2 N2
But N2 = 1 so we can take N1 = N
Hence I1 N = I2
Power loss in secondary P = I22R
Where R = resistance of the metal piece.