Question

Electric potential due to a positive and negative charge

Answer 1

Electric Potential Energy (U) and Electric Potential (V): (Notes from C. Erkal’s lectures PHYS 221)Consider a parallel plate capacitor that produces a uniform electric field between its large plates.This is accomplished by connecting each plate toone of the terminals of a power supply (such as abattery).Figure 1: An electric field is set up by the chargedplates separated by a distance l.The charges on the plates are +Q and –Q.Figure 2: An electric charge q is moved from point A towards point B with an external force T against the electric force qE.Figure 3, 4: When it is moved through a distance d, its potential energy at the point B is qEd relative to the point A.Figure 5: When released from B (T = 0), it will accelerate toward the lower plate.As it is moving toward the lower plate, its potential energy decreases and its Kinetic energy increases.When it reaches the lower plate (where we can choose the Potential energy to be zero), its potential energy at A is completely converted to Kinetic Energy at point B:Note that qEd is the work done by the field as the charge moves under the force qE from B to A.Here m is the mass of the charge q, and v is its velocity as it reaches point A.Here we assumed that electric field is uniform!Work done by E field:Let’s remember Kinetic Energy-Work theorem (Work Energy principle):where we introduced the concept of potential energy and conservative force ( a force under which one can define a potential energy so that the work done only depends the differences of the potential energy function evaluated at the endpoints).l hope this answer is helpful to you