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Numerical from Electrostatics

Three point charged lie along the x axis in a vacuum: charge 1 in the middle, with charge 2 to the left, and charge 3 to the right. The magnitude of charge 1 is +3 microcoulomb, the magnitude of charge 2 is -4 microcoulomb, and the magnitude of charge 3 is -7 microcoulomb. The distance between charges 1 and 2 is 20 cm, while the distance between charges 1 and 3 is 15 cm. Determine the magnitude and direction of the net electrostatic force on charge 1.

Asked Tammy

How protons became closer during Big bang process?

English: Schematic representation of a nucleus...
English: Schematic representation of a nucleus as an ensemble of neutrons and protons (Photo credit: Wikipedia)

I know that strong nuclear force is a short-ranged force. So, I would like to know how protons became closer during Big bang process. Is it because of very high temperature and pressure during this ?
Please explain me.
Thanks in advance.


In nuclear fusion the nucleons (protons and neutrons come closer because of their high energies. When they come closer to each other in the order of distances of fermi (10^-15 m) nuclear force – the strongest force in nature, comes into play

… Awaiting responses

Why there is a 4(pi) in Coulomb’s law?

Why there is a 4π in Coulomb’s law?

Asked Rick Ghosh


This is a consequence of geometry.

Please remember that Coulomb’s law is stated originally for point charges  at rest. By symmetry, a point charge should exert equal force on a test charge at all points equidistant from it, which constitute a spherical shell of surface area 4πr2.

This consideration itself suggests the inverse square relation ship as well as the need for 4π.

That was actually my explanation for it.

The term 4π was not there when Coulomb’s law was first stated in cgs system. The term 4π was introduced in SI on rationalization of units based on Maxwell’s equations of electromagnetism.

But I feel that  my earlier explanation is simple and convincing.

Hope you got it.

Further discussions are welcome.

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