Electric Field

Electric Field

A charged particle cannot directly interact with another particle kept at a distance. A charge produces something called an electric field in the space around it and this electric field exerts a force on any other charge (except the source charge itself) placed in it.

Thus, the region surrounding a charge or distribution of charge in which its electrical effects can be observed is called the electric field of the charge or distribution of charge.

Thus, the region surrounding a charge or distribution of charge in which its electrical effects can be observed is called the electric field of the charge or distribution of charge.

The electric field can also be visualised graphically in terms of ‘lines of force’.

Note that all these are functions of position r (x,y,z) . The field propagates through space with the speed of light, c. Thus, if a charge is suddenly moved, the force it exerts on another charge a distance r away does not change until a time r /c later.

Electric Field Strength ( E)

Like its gravitational counterpart, the electric field strength (often called electric field) at a point in an electric field is defined as the electrostatic force F_e per unit positive charge. Thus, if the electrostatic force experienced by a small test charge q₀ is F_e, then field strength at that point is defined as

The electric field is a vector quantity and its direction is the same as the direction of the force F_e on a positive test charge.

The SI unit of electric field is N/C.

Here, it should be noted that the test charge q₀ should be infinitesimally small so that it does not disturb other charges which produces E.

With the concept of electric field, our description of electric interactions has two parts. First, a given charge distribution acts as a source of electric field. Second, the electric field exerts a force on any charge that is present in this field.

Suppose there is an electric field strength E at some point in an electric field, then the electrostatic force acting on a charge +q is qE in the direction of E, while on the charge – q it is qE in the opposite direction of E.