IIT JEE , AIEEE Forum - Articles Category , Community shelf - Electrostatics-I

chirag

I am giving electrostatics notes in parts to facilitate reading and avoid overdose.

Electrostatics (also known as Static Electricity) is the branch of physics that deals with the forces exerted by a static (i.e. unchanging) electric field upon charged objects. Electrostatics involves the build-up of charge in objects due to contact between (generally) non-conductive surfaces. These charges are generally built up through the flow of electrons from one object to another. These charges then remain in the object until a force is exerted that causes the charges to balance e.g. the familiar phenomenon of a static 'shock' is caused by the neutralization of charge built up in the body from contact with non-conductive surfaces.

The electrostatic approximation

The validity of the electrostatic approximation rests on the assumption that the electric field is irrotational:

$\vec{\nabla} \times \vec{E} = 0$

From Faraday's law, this assumption implies the absence or near-absence of time-varying magnetic fields:

${ \partial \vec{B} \over \partial t} = 0$

In other words, electrostatics does not require the absence of magnetic fields or electric currents. Rather, if magnetic fields or electric currents do exist, they must not change with time, or in the worst-case, they must change with time only very slowly. In some problems, both electrostatics and magnetostatics may be required for accurate predictions, but the coupling between the two can still be ignored.

Electrostatic potential

Because the electric field is irrotational, it is possible to express the electric field as the gradient of a scalar function, called the electrostatic potential (also known as the voltage). Thus, the electrostatic potential ? is related to the electric field

E

by the equation:

$\vec{E} = - \vec{\nabla} \phi = \frac{kQ}{r}$

Rate the post if u liked it...!!!

Ask & Discuss Questions with Community & Experts

Electrostatic potential