Ring of charge probed with Atomic Force Microscopy dielectric tip.

Abstract

We consider a dielectric sphere in the presence of a charged ring and derive expressions for their interaction force. New mathematical closed form expressions for electrostatic problems involving dielectric objects are always interesting, both for their intrinsic foundational value, and also for their practical use as test beds for numerical solutions. The chosen geometry is motivated by the importance to probe charged rings with Atomic Force Microscopy dielectric tips. The interaction forces obtained are further analyzed to identify notorious features of the force versus separation curves. This analysis provides practical guidelines to measure charge and size of rings from experiments.