FUNDAMENTALS

INTENSITY OF FIELD:

There is an electrostatic field due to any charged body and the intensity of this

field is taken as the force on unit charge.

The intensity of field at any given point due to an electrostatic charge is given by

E= q / 4╥ﻉ○ d² V/m

AMPERE

The value of the ampere is defined as that current which, when flowing in each

of the two infinitely long parallel conductors in a vacuum, separated by one

meters from centres, causes each conductor to have a force acting upon it of

2 x 10−² N/m lenghth of conductor.

DIELECTRIC FLUX:

The field due to a charge as referred to the above is assumed to be due to

imaginary tubes of force similar to the magnetic lines of force and the tubes are

the paths which would be taken by a free unit charge if acted on by the charge of

the body concerned.

By means of these tubes we get a dielectric flux density of so many tubes of

Force per square metre of area. Let us take a spere of 1 metre radius and give it

unit charge of electricity. We get a dielectric flux density on the surface of sphere

of unit = one tube of force per square centimeter. The total number of tubes of

force will be equal to the surface area of the sphere=4 ╥

For any charge ‘q’ at a distance ‘r’ the dielectric flux density will be

D = q/ 4 ╥ŗ² C/m²

There fore intensity of electric field is E = q/4 ╥ﻉ○ﻉŗ² i.e E= D/ﻉŗ○