# Electric vs Gravitation

Coulomb’s law: Fe=kQ1Q2/d2

Newton’s law of gravitation: Fg=GM1M2/d2

The similarities between Newton’s law of gravitation and Coulomb’s Law are hard to miss. But there is one major difference between them: while there is only one type of mass, there are two types of charges: positive and negative. While all gravitational forces are attractive, electric forces is attractive between two unlike charges, but repulsive between two like charges. And this has made all the difference.

If you think about it, $k=\frac{1}{4\pi {{\varepsilon }_{0}}}=8.99\times {{10}^{9}}\text{ N }{{\text{m}}^{2}}\text{ }{{\text{C}}^{-2}}$ is a much larger constant than $G=6.67\times {{10}^{-11}}\text{ N }{{\text{m}}^{2}}\text{ k}{{\text{g}}^{-2}}$. In addition, one mole of electrons make up a charge of ~104 C but only a mass of ~10-4 kg. So the obvious question is: shouldn’t electrical forces always dominate over gravitational forces under all situations?

Well, we have to realize that it is very difficult to hold a large amount of unbalanced charges in a small volume because LIKE CHARGES REPEL. Gravitation has no such problem since it is always attractive. For this reason,

• Gravitational forces dominate the study of astronomy. Massive stars planets can be formed through gravitational pulls. The orbits of planets and comets are also governed by gravitational forces. Heavenly bodies, even though they contain lost of electrons and protons, are neutral in charge to one another.
• Electric forces dominate the study of chemistry. At atomic distances, the localised charges of electrons and ions provide the binding forces for the formation of molecules. Electric attraction AND repulsion provide the explanations for the properties of solids, liquids and gases. The gravitational attraction between the mass of individual electrons and ions are negligible.