A tiny insulating bead of mass carries a charge of
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A tiny insulating bead of mass 2.0g carries a charge of −1.0μC. The bead is released from rest at a point that is 5.0×10−2m from a fixed point charge of +8.0μC in vacuum. Ignore all forces except the electrostatic interaction between the two charges. Take the zero of electric potential energy at infinite separation.
(a) Determine the electric potential energy of the system at the moment the bead is released.
(b) Calculate the kinetic energy of the bead after it has moved very far from the fixed charge (effectively at infinite separation).
(c) Find the speed of the bead when it is very far away.
(d) Explain, using energy conservation, why your answers to parts (a) and (b) must have opposite signs and how this relates to the nature of the force acting on the bead.