Time-dependent interaction across two conducting spheres in an applied electrostatic field

•Time-dependent interaction has been measured from experiment.•A small amount of charges on sphere can influence electric interaction significantly.•The sphere is charged through the conductivity of the alumina tube.•The fall of the interaction is caused by the electric breakdown in the gap.•Mirror image charge method is used to calculate the case that the sphere is charged.

Charged particles exist widely in variety of technological areas as well as in nature. Even a weak charge on the particles can significantly influence their electric interaction. We investigated the phenomenon of time-dependent electric interaction between two conducting spheres in an electrostatic field. A mirror-image method was developed to analyze this system, and the fundamental role of the charges on the spheres was studied. We concluded that charges conducted to the lower sphere through the alumina tube used in our system play a main role in determining the time-dependent interaction, whereas the influence from air ions is negligible.