is seen as increased heat non polymer polymers such polyolefins may not be heated dielectrically because of the dearth of a positively and a negatively changed portions within their molecular structures the energy delivered to the polar polymer sheet by an rf field applied by a pair of electrodes on opposite sides of the sheet is given by the expression tan u03b4 dielectric loss tangent property of the sheet material being heated for a given field strength and a fixed frequency the power density p can be calculated the local field strength e in the polymer sheet is a function of the applied voltage and the geometry of the electrode for a constant applied voltage the local field strength e is approximately inversely proportional to the spacing between the electrodes the temperature rise t per cm 3 in the polymer sheet can then be calculated from where t is time in seconds m is the mass of the sheet portion being heated and c is the specific heat of the heated polymer sheet since p is proportional to the square of the electric field strength an effective way of controlling temperature is by increasing or decreasing the field strength e further since e is generally inversely proportional to the mutual spacing of the electrodes such temperature control can be effected through.