Two equal and opposite point charges +q and –q are fixed at positions (–a, 0) and (a,…
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
Two equal and opposite point charges +q and –q are fixed at positions (–a, 0) and (a, 0) on the X-axis, forming an electric dipole.
(a) Sketch qualitatively the equipotential surfaces (1) in the plane y=0 containing the charges, and (2) along the line perpendicular to the dipole axis through the midpoint O. Label at least three different potential values on each sketch.
(b) Consider two points P and R on the dipole axis such that OP=5a and OR=15a. Compare the separation between successive equipotential surfaces near P and near R, and hence conclude which point experiences the stronger electric field.
(c) Explain why no work is required to move a test charge from one point to another along any single equipotential surface of the dipole.