Effects of electric field-induced versus conventional heating (Vol. 43 No. 1)

image Study of mobile phone electric field shown no extraordinary heating

The effect of microwave heating and cell phone radiation on sample material is no different than a temperature increase, according to the present work.

Richert and coworkers attempted for the first time to systematically quantify the difference between microwave-induced heating and conventional heating using a hotplate or an oil-bath, with thin liquid glycerol samples. The authors measured molecular mobility and reactivity changes induced by electric fields in these samples, which can be gauged by what is known as configurational temperature. They realised that thin samples exposed to low-frequency electric field heating can have a considerably higher mobility and reactivity than samples exposed to standard heating, even if they are exactly at the same temperature. They also found that at frequencies exceeding several megahertz and for samples thicker than one millimetre, the type of heating does not have a significant impact on the level of molecular mobility and reactivity, which is mainly dependent on the sample temperature. Actually, the configurational temperatures are only marginally higher than the real measurable one.

Previous studies were mostly fundamental in nature and did not establish a connection between microwaves and mobile phone heating effects. These findings imply that for heating with microwave or cell phone radiation operating in the gigahertz frequency range, no other effect than a temperature increase should be expected.

Since the results are based on averaged temperatures, future work will be required to quantify local overheating, which can, for example, occur in biological tissue subjected to a microwave field, and better assess the risks linked to using both microwaves and mobile phones.

Heating liquid dielectrics by time dependent fields
A. Khalife, U. Pathak and R. Richert, Eur. Phys. J. B 83, 429-435 (2011)