Coulomb's Law[]
Any two point charges exert a force on each other that is proportional to the product of their charges, and inversely proportional to the square of the distance between them. This interlinks with the force of gravity as its strength weakens by the inverse square law
as well.
Coloumb's Law where Ke is equal to 1 over 4pi Epsilion
This is Coulomb's law where Q1 and Q2 are the charges excerting a force on each other and K is the electric constant.
How Gravitational and Electric fields compare[]
The table below summarises some of the similarities between gravitational and electric fields. As you can see the similarities shown indicate that these fields have many aspects eg. equations that are almost the same but just take different quantities into account.
| Gravitational fields | Electric fields |
|
All gravitational fields field strength g= F/m ie. field strength is force per unit mass |
All electric fields field strength E=F/Q ie. field strength is force per unit charge |
|
Units F in N, g in N kg -1 or ms-2 |
Units F in N, E in N C-1 or V M-1 |
|
Uniform gravitational fields parallel field lines g= constant |
Uniform electric fields parallel field lines E= V/d= constant |
|
Spherical gravitational fields radial field lines force given by Newtons law: F=GMm/r(squared) field strength is therefore: E=Gm/r(squared) |
Spherical electric fields radial field lines parallel field lines force given by coulombs law: F=kQq/r(squared) field strength is therefore: E=kQ/r(squared) |
|
Vector forces only gravitational attraction, no repulsion |
Vector forces both electrical attraction and repulsion (possible because of positive and negative charges) |