9 will be driven at the higher frequency f 2 50 khz which is higher than the frequency f 1 and will supply a high frequency current at frequency f 2 to inductance heating coil 12 and pan 11 will be inductance heated next the relation of turn ratio to frequency ratio and to input voltage ratio and their significance to this invention will be described this invention has been made to keep constant the input power to the induction heating coil irrespective of the selection of the input voltage the number of turns of induction heating coil 12 and a value of the skin resistance of the pan even when the skin resistance peculiar to pan 11 is different in this case pan 11 acts as a secondary coil and its number of turns is considered to be 1 next the maintenance of almost equal values of the input power of inductance heating coil 12 of this electromagnetic induction cooking apparatus even when the material of pan 11 is changed from iron for example to aluminum with widely differing skin resistances will be described in fig3 a and 3b there are illustrated the waveforms of the input voltage ei and output voltage e 0 of inverter 9 in this example it is assumed that there is no voltage drop between the inverter input and output and load current i l the input power pai for one period t f of inverter 9 is given by equ2 where r l is load resistance as seen from the input terminal of inductance heating coil 12 the actual input power pbi when input voltage ei is not sufficiently smoothed and contains a ripple of the frequency of the commercial ac power is given by the following equation equ3 in the.