Torque exerted by a moving electric charge on a stationary electric charge distribution

Abstract

The interaction between a moving electric charge and a stationary electric charge distribution is considered. It is shown that the interaction involves not only an electric attraction or repulsion but also a heretofore unreported electric torque exerted by the moving charge on the stationary charge distribution. The torque is associated with the asymmetry of the electric field of the moving charge and is present even if the stationary charge distribution is highly symmetrical, such as a uniformly charged sphere, for example. As a result of the torque, the stationary charge distribution is set in rotation. The rotating stationary charge distribution creates a magnetic field and an induced electric field that act on the moving charge thus further contributing to the complexity of the interaction. Two types of moving charges are considered: a point charge moving with constant speed along a straight line and a point charge moving with constant speed along a circular orbit. The torques exerted by these charges on stationary charge distributions in the shape of a small circular ring, small disc, and small sphere of uniform charge density are computed and some consequences of these torques are discussed. The possibility of the existence of a similar interaction effect in gravitational systems is also considered.