Electric Charges and Fields Mind Map

Electric charge is a fundamental property of matter due to which bodies exert electric forces on one another. It exists in two types, positive and negative, and any observable charge is an integral multiple of the elementary charge: q = ne.

When a question mentions loss of electrons, charge is positive; when it mentions gain of electrons, charge is negative. Always attach the correct sign and SI unit.

Coulomb's law states that the electrostatic force between two stationary point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them, acting along the line joining the charges.

For numerical questions, first convert microC to C and cm to m. Use signs to decide attraction or repulsion, but use magnitudes for force magnitude.

Electric field at a point is the electrostatic force experienced per unit positive test charge placed at that point: E = F/q0. It is a vector quantity directed along the force on a positive test charge.

In diagrams, arrows on field lines matter. For a positive source charge arrows go outward; for a negative source charge arrows go inward.

An electric dipole is a pair of equal and opposite charges separated by a small distance. Its dipole moment is p = q(2a), directed from negative charge to positive charge.

In derivations, clearly mark axial point, equatorial point, distances from both charges, and final direction of net field. Direction carries marks in dipole questions.

Electric flux through a surface measures the total electric field passing normally through that surface. For a closed surface, Gauss's law states that the net electric flux equals the enclosed charge divided by ε0: Φ = q_enclosed/ε0.

Before applying Gauss's law, ask two things: what charge is enclosed, and whether symmetry lets you take E outside the integral.

Applications of Gauss's law use symmetry to find electric field due to charge distributions such as an infinitely long line charge, an infinite plane sheet, and a uniformly charged spherical shell.

Name the Gaussian surface in derivations: cylinder for line charge, pillbox for sheet, concentric sphere for shell. This shows why the flux integral becomes simple.