PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A small bead of mass 5.0g carries a charge of −2.0μC. The bead is released from rest at a height of 2.0m above a large horizontal conducting plate which is maintained at a uniform electric potential gradient of 2000V m−1 directed upward (i.e.\, potential increases with height). Neglect air resistance.
(i) Calculate the potential difference between the initial position of the bead and the plate.
(ii) Taking gravitational potential energy into account, determine the speed with which the bead strikes the plate. Use g=9.8m s−2.
(iii) Comment on whether the electric force or the gravitational force is dominant in deciding the final speed, supporting your answer with numerical comparison of the magnitudes of work done by each force.