Electrostatics, medicine, and metal spheres

Electrostatics have an important role in the field of medicine. Anodes, cathodes, and electric potential sources are heavily relied upon in X-RAY machines, heart-rate monitors, electrostatic therapy, protein modeling, and a plethora of devices used in hospitals and clinics. The fundamental aspects of electrostatics are often applied to a variety of physician practices, and they are currently being explored by a biomedical engineering research team interested in developing a new device involved in pain management.

In a physics lab, this team takes two metal spheres A and B of identical mass and hang them from insulating strings of length L. The researchers can then electrically charge the spheres independently. After one such trial, it is seen that the two spheres attract each other so that they hang at rest with their centers a distance D apart and at an angle of θ from the vertical.

Figure 1. A diagram of the laboratory apparatus the team is using.