Electric Charges and Field Summary

• Electric charge is a basic property of all matter.

• Unlike charges attract, like charges repel.

• Conductor allow flow of electric charges through them while insulators don't.

• Electric charges have three basic properties

(a) Additivity (b) Quantisation (c) Conservation

• Coulomb's law: the Electrostatic force of interaction between two point electric charges is directly proportional to the product of the charges, inversely proportional to the square of the distance between them and act along the straight line joining the two charges.

• Superposition Principle: The electric intensity at a point due to several charges is the vector sum of electric intensities produced by each charge individually in the absence of other charges.

• Electric field is the region of space around a charge or a system of charges within which other charged particles experiences an electrostatic force.

• Electric field line is an imaginary straight or curved path along which a unit positive charge is supposed to move when free to do so in any electric field.

• Electric dipole is a pair of equal and opposite point charges separated by a small distance.

• In a uniform electric field, a dipole experiences a torque, and net force becomes zero.

• Various properties of Electric field lines:

(a) lines are continuous

(b) two field lines cannot cross each other.

(c) Field lines start from positive charge to negative and cannot form closed loops.

• Gauss' law states that the surface integral of the electric field intensity over any closed hypothetical surface (Gaussian surface) is  equal to 1/ Î₀ times the net charge enclosed within the surface.