Electric Field

The potential of electric field of a point charge:-
If potential 0-level is chosen in infinity The electric field potential at a point in space is equal to the amount of work we done by electric force to move the test charge from the point in question to infinity, divided by charge. The electric potential created by a point charge Qsource, at a distance r from the charge (relative to the potential at infinity), can be shown to be:

Electric field:-
• Intensity of an electric field E (or strength of an electric field or electric field) is vector characteristic. It is defined as the ratio of the force F acting upon the test charge to the magnitude of the test charge.

• The electric field of a point charge can be obtained from Coulomb's law.
• The magnitude of electric field produced by point charge Qsource at a distance r from this charge (in a point of M is where the electric field is defined).

Field lines:-

• An electric field has both magnitude and direction. The distribution of an electric field in space is visually represented by the intensity lines (or lines of force or field lines). Electric field-lines are drawn according to the following rules:
The direction of the electric field is everywhere tangent to the field-lines, in the sense of the arrows on the lines. The magnitude of the field is proportional to the number of field-lines per unit area passing through a small surface normal to the lines.

• The lines of force of a potential electric field (electrostatic field) that is created by electric charges originate on positive charges and terminate on negative charges. The electric field is stronger where the field lines are close together than where they are farther apart.

Electric Dipole:-

• An electric dipole is a pair of point electric charges of equal magnitude but opposite sign, separated by some small distance.
• The distribution of the charge in a dipole can be characterized by a parameter called the dipole moment p. The dipole moment is a vector which is directed from the negative charge towards the positive charge and is defined as:

Electrostatics

Electrostatics:-

• Electrostatics is the study of electric charge at rest.
(Or more or less at rest, in contrast with current electricity.)


Electrical Charges:-

• Electric charge is a fundamental property of matter.

Two types of electric charges:
• Positive charge - every proton has a single positive charge.
• Negative charge - every electron has a single negative charge.


• An object with an excess of electrons is negatively charged.
• An object with too few electrons (too many protons) is positively charged.
• An object with the same number of electrons and protons is neutral.


• Like charges repel.
• Opposite charges attract.

Elementary Charges:-

• Protons carry the smallest positive charge.
• Protons and uncharged neutrons generally reside in an atom’s nucleus.
• Protons are held in the nucleus by the strong force.

• The smallest negative charge is the charge on the electron.
• In normal atoms, electrons orbit the nucleus.
• The electric force between electrons and protons supplies the centripetal force to keep electrons in the atom.

• The charges carried by the proton and electron are equal in size.
• The mass of the proton is about 2000 times the mass of the electron.


Units of Charge:-

• The SI unit of charge is the Coulomb.

1 Coulomb = the charge of   (6.24 x 10^18)   electrons.

e   =   (1.602 x 10^-19)   C


Charge is Conserved:-

• Electric charge is conserved:
– Electric charge moves from one place to another: (no case of the net creation or destruction of electric charge has ever been observed.)
• In solids, only electrons can move.
• In liquids, gasses, and plasma, both positive and negative ions are free to move.

Electrical Charge

Electrical Charge:-

Electrical charge is an electrical property of matter that exist because of an excess or deficiency of electrons.

The charge of an electron and that of a proton are equal in magnitude.

Charge is symbolized by letter ‘Q’.

Static Electricity: the presence of a net positive or negative charge in a material.

Electrical charge Q is measured in coulomb, symbolized by ‘C’. One coulomb is the total charge possessed by 6.25 X 10¹⁸ electrons.

A single electron has a charge of 1.6 X 10^-19 C.

Q  =  number of electrons    /    6.25 X 10¹⁸ electrons/C

There is a force (F) between charges. Like charges repel; unlike charges attract:-

The force is directly proportional to product of two charges and inversely proportional to square of distance. This force, called an electric field.