PURPOSE: To increase a static capacitance and obtain a large static induction power which is proportional to the static capacitance by a method wherein an insulated lead wire is composed of a multiple-conductor which is constituted by arranging a plurality of element conductors property to obtain a required equivalent diameter.

CONSTITUTION: A multiple-conductor F which is constituted by arranging a plurality of element conductors (f). By employing the multiple-conductor F as insulated lead wire, the large equivalent diameter De of the insulated lead wire is obtained. Therefore, a static capacitance can be increased and, further, the distance of the insulated lead wire can be reduced. It is to be noted that, if respective distances S between the element conductors (f) are made to be approximately equal to each other, mutual influences between the element conductors (f) can be reduced, so that the degradation of the static capacitance can be suppressed. Particularly, in the case of the multiple- conductor F composed of the element conductors (f) which are arranged linearly, respective induced voltages are equal to each other when the respective distances S between the element conductors are approximately equal to each other, so that a maximum power can be obtained. By this constitution, a large power can be obtained even if the distance of the insulated lead wire is small.