Electrostatics Basic Theory:

Electrostatics is a branch of science which deals with static electricity i.e, electricity at rest such as stationary charges on conductors and the laws that govern them.

Electric Filed:

The space around the charge experiences stress and when another charge is brought near to the stress zone, force will be created on the charge which was brought. The region of space in which stress exist can be defined as electric (or dielectric or electrostatic) field. The stress in the space is represented by lines of force.

Field Strength or Field Intensity:

The force experienced on a unit point charge placed at any point in an electrical field is known as electrical field strength or field intensity or electric intensity at that point. The field strength is represented by E and is measured in newtons per coulomb of charge. This is a vector quantity (i.e, have direction as well as magnitude)

Electric Flux Density:

Electric flux density is defined as the number of tubes of force per unit area emanated normally from the surface. Electric flux density is represented by letter D and is measured in coulombs/m2.

Potential:

It is the work done to bring the unit point charge from infinity to that point is defined as potential

Potential Difference:

Potential Difference between two points in an electrical field is defined as the work done in moving a unit positive charge from point of lower potential to the point of higher potential

Potential Gradient:

Potential Gradient is defined as the rat if change of potential with distance measured in the direction of electrical force. Electric intensity at any point is equal to the negative potential gradient at that point. Electrical intensity at any point is equal to the negative potential gradient at that point

Equipotential Surface:

The surface in an electric field at right angles to the lines of force or flux everywhere is equipotential surface.

Breakdown potential:

When the potential applied across the dielectric medium or insulating medium gradually increased, a point will be reached where the insulation of the medium gets damage and starts conducting. This potential gradient at which insulation just gets breakdown is known as breakdown potential or dielectric strength of an insulator material. It is measured in terms of volts / mm

Potential and Electrical Field Intensity Inside Sphere:

It was experimentally found that, when a charge is given to the sphere or to any body, charge resides only on the outer surface of the body. Inside the body or within the body conducting body charge, flux and field intensity are zero. All the points within the surface area at the same potential as the points on the charge.

Coulomb’s Law of Electrostatics:

When two charged bodies are placed near to each other, mechanical force is experienced on them. According to Coulomb’s first law charges of same nature repel one another and that of opposite nature attract i.e, force experienced between two bodies charged with the charges of same nature will be force of repulsion and force experienced between tow bodies charged with charges of opposite charges attract each other

According to Coulomb’s second law the force between the two charges

• Is directly proportional to the product of charges
• Inversely proportional tot the square of distance between them
• Depending on the nature of medium surrounding the charges