Coulomb's Law: Equality of Charges in Different Size Balls

[NotaPhysicsMan]

Ok,

Suppose I have two balls that come into contact to make their charges say q1=q2. Would the charges be equal if the balls were of different size?

I'd say yes, because mass is not relevant in Coulomb's law.

 

[Andrew Mason]

Ok,

Suppose I have two balls that come into contact to make their charges say q1=q2. Would the charges be equal if the balls were of different size?

If the balls are conductors, the charges on each ball will move until all charge is at the same electrical potential. Electrical potential on the surface of a conducting sphere is:

$$V = \frac{Q}{4\pi\epsilon_0R}$$

If the balls are of different size (radius) but equal charge, the potentials will not be the same. So when they touch the charges will move so that the potential V for each is the same (ie. a sphere half the radius as the other, will have half the charge as the other).

AM

 

[wais]

The law only takes into account the distance between the charges and the magnitude of the charges themselves. So, even if the balls are of different sizes, as long as their charges are equal, the force between them will still follow the inverse square law and be proportional to the product of the charges. The size of the balls may affect the distribution of the charges, but it won't change the overall equality of the charges.