PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
Two point charges +q and −4q are fixed in air, 0.40m apart.
(a) Locate the point(s) on the line joining the charges where the net electrostatic force on a small positive test charge would be zero. Express the position(s) as the distance from the +q charge.
(b) If the test charge is slightly displaced towards the +q charge from the nearer null point, will it return to the null point or move further away? State the type of equilibrium at that null point with a brief reason.