LINES . . Electric Field The interaction between two charges is determined by Coulomb’s law. How does the interaction itself occur?
Consider a point charge kept at a point in space. If another point charge is placed at some distance from the first point charge, it experiences either an attractive force or repulsive force. This is called ‘action at a distance’. But how does the second charge know about existence of the first charge which is located at some distance away from it?
To answer this question, Michael Faraday introduced the concept of field . According to Faraday, every charge in the universe creates an electric field in the surrounding space, and if another charge is brought into its field, it will interact with the electric field at that point and will experience a force. It may be recalled that the interaction of two masses is similarly explained using the concept of gravitational field (Refer unit , volume , XI physics). Both the electric and gravitational forces are non-contact forces, hence the field concept is required to explain action at a distance.
Consider a source point charge q located at a point in space. Another point charge q o (test charge) is placed at some point P which is at a distance r from the charge q . The electrostatic force experienced by the charge q o due to q is given by Coulomb’s law. kqq qq π e where k = π e The charge q creates an electric field in the surrounding space within which its effect can be felt by another charge.
It is measured in F = . × – N kq = × = . × – N From the figure, the angle θ = o . In terms of the components, we have j cos sin θ θ j F i j cos sin θ θ j Then the total force