The quantitative measurement of an electrostatic charge on a housefly by capacitor techniques

Abstract

The quantitative measurement of an electrostatic charge on the body of a living housefly was demonstrated. The mechanical facility for doing this consisted of a large air-type electrical capacitor. A n interior, d.c. electric field gradient of 1,250 volts/cm. was induced in the air-gap separating the two capacitor plates. Single, charged flies suspended by small nylon fibers between the capacitor plates were subsequently deflected toward one of the plates. The amount of deflection was dependent upon the charge and mass of the insect, the plate separation and voltage, and the acceleration of gravity. These factors were interrelated as demonstrated by the derivation of the fly charge equation. Assumptions in the theory required calibration of the charge measuring instrument against a standard. This was accomplished by determining the fly charge by two techniques, and subsequently relating the two charge magnitudes. The research showed that electrostatic charge measurements can be successfully made and that doing so requires some experience and caution. Utility of the developed charge measuring technique and facility was demonstrated with several experiments. One such experiment showed that the housefly exhibits a variable capacitance nature. Detailed studies showed that the varying capacitance nature could not be attributed to: 1) physical exercise of the fly, 2) change due to the drinking of water by the fly, or 3) changes that might take place within 10 minutes after gassing the fly in poisonous fumes. Another experiment showed that time periods of an observed "oscillatory effect" from flies in the electric field were related to the times required to kill the flies in a gas chamber. This response, in part, implied that respiration frequencies were the effects being measured in the electric field. All living flies observed showed the "oscillatory effect". Dead flies did not show this phenomenon.