Zusammenfassung
The biological effect of extremely low frequency (ELF, 0-300 Hz) electric field is a familiar issue
such as the cases of high-voltage power transmission lines and household electrical appliances.
Among several possible mechanisms, the stimulation of the body surface has been recognized as an
apparent biological effect of the ELF electric field. We perceive the stimulation of electric field as a
somatic sensation. The safety standard for the field exposure has been established on the basis of the
perception threshold of the electric field in many countries, including Japan. However, there are many
uncertain points in the field perception, and the safety standards are different across different countries.
Therefore, the objective study to clarify the mechanism of the field perception particularly in
commercial frequencies has been required.
We have studied the mechanism of the field perception, and found that the hair movement caused by
the electric force was a significant factor for the body surface stimulation in electric field exposure.
We modeled the body hair in an electric field, and theoretically analyzed the hair movement for DC
field exposure. However, the hair movement must be different in AC field. Therefore, in the present
study, we expand the previous study to analyze the body hair movement in AC electric field exposure.
The hair movement in AC field was newly formulated in the equation of motion, or in a differential
equation. The equation was solved by treating the nonlinearity appropriately. An analytical solution
was obtained in a closed form. Using the solution, we could analyze the hair movement in AC field
exposure. When the electric field with the frequency f is applied to a hair on the body, it stands up
exponentially while vibrating in the frequency of 2f
When humidity changes, the dielectric constant of the hair changes, and the electric force on the hair
changes accordingly. Thus, the perception of electric field can be different in different humidity. This
might be one of the reasons why the safety standards are different in different countries. The effect of
this difference was examined using the solution obtained. The hair movement was compared when the
relative dielectric constant of the hair increases from I 0 to 80 which correspond to the relative
humidity of 50% and 90%, respectively. In the higher humidity, the hair stands up more rapidly and
reaches the larger final angle with the greater vibration amplitude.
To examine the validity of this analysis, the hair movement in electric field exposure was measured in
the experiment using an ultra-fast video camera. The results of experiments agreed well with those of
theoretical analysis using the solution obtained. The greater movement of body hair was confirmed in
the atmosphere with the higher humidity. In this way, the validity and the usefulness of the solution
were verified both in computer simulation and experiment. These results also suggest that we need to
take the effect of humidity into account in establishing the safety standard for AC field exposure based
on the perception threshold.
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