Arrangement of Charge
Arrangement of Charge
The electrostatic force determines the arrangement of charge on the surface of conductors. This is possible because charges can move inside a conductive material. When we place a charge on a spherical conductor the repulsive forces between the individual like charges cause them to spread uniformly over the surface of the sphere. However, for conductors with irregular shapes, there is a concentration of charge near the point or points of the object.
Notice in the figure below that we show a concentration of charge with more \(-\) or \(+\) signs, while we represent uniformly spread charges with uniformly spaced \(-\) or \(+\) signs.
Did You Know?
This collection of charge can actually allow charge to leak off the conductor if the point is sharp enough. It is for this reason that buildings often have a lightning rod on the roof to remove any charge the building has collected. This minimises the possibility of the building being struck by lightning. This “spreading out” of charge would not occur if we were to place the charge on an insulator since charge cannot move in insulators.
Charge on conductors
When two identical conducting spheres on insulating stands are allowed to touch they share the charge evenly between them. If the initial charge on the first sphere is \({Q}_{1}\) and the initial charge on the second sphere is \({Q}_{2}\), then the final charge on the two spheres after they have been brought into contact is:
\[Q = \frac{{Q}_{1} + {Q}_{2}}{2}\]
This lesson is part of:
Electric Charges and Fields