Electrostatics

INTRODUCTION

The static electric field could also be termed as electrostatics. In electrostatics the  phenomenon associated with static charge or electricity at rest are dealt with. An atom in normal condition is electrically neutral because, positive charges on protons and negative charges on electrons are equal. If a normal atom, however, accepts negatively charged electrons somehow, then the atom is said to be negatively charged. On the other hand if electrons are removed somehow from a normal atom, then the atom is said to be positively charged. Thus negatively charged body contains excess of electron and positively charged body is in deficiency of electrons and net excess or deficiency of electrons into body is known as charge. 

When a glass rod is rubbed with silk acquires a positive charge or positively electricity where as a hard rubber rod rubber with cat’s fur acquires a negative charge or negative electricity. In doing so, electrons are detached from glass rod and picked up by silk and hence former becomes positively charged where as latter becomes negatively charged as electrons, in this case, are picked up by hard rubber from cat’s fur. The net positive charge on glass- rod is equal to the net negative charge on silk and so on. Further, two positively charged bodies repel each other and so are the two negatively charged bodies but a positively charged body and a negatively charged body attracts each other which establish the fact that like charges repel and unlike charge attract each other.

There are two types of charges

(a) Positive charge

(b) Negative charge

NOTE:

Stationary charge posses Electrostatic field and moving charge posses Magnetic field.

ELECTRIC FIELD

The space up to where another charges experiences force of attraction or repulsion, is called electric field.

COULOMB’S LAW

According to Coulomb’s law, The force of attraction or repulsion between two point charges is directly proportional to the square or magnitude of charge and inversely proportional to the square of distance between them.

This theorem was proposed by Charles Augustin De Coulombs in 1785.

If two charges q1 and q2 are separated by a distance r then, Mathematically we can say

F∝ |q1 q2|

F∝ 1/ r²

F= K q1 q2/ r² ; where K= constant =1/ 4π∈ (for medium)

1/ 4π∈ο (for air )=9×10^9