Comprehensive notes for Chapter 9 Electrostatics and Current Electricity. Covers Coulomb's Law, Electric Fields, Gauss's Law, Ohm's Law, Kirchhoff's Rules, and more.
Statement: The force between two point charges is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them (F = k q1q2/r²).
Vector Form: Force is mutual; F12 = -F21.
Effect of Medium: Presence of a dielectric reduces the force by a factor of 𝜀r (Relative Permittivity).
Electric Field (E): Force per unit positive charge (E = F/q). Unit: N/C or V/m.
Electric Potential (V): Work done in bringing a unit positive charge from infinity to a point. Unit: Volt (V).
Potential Gradient: E = -ΔV/Δd. Electric field intensity is the negative gradient of potential.
Statement: The total electric flux through any closed surface is 1/𝜀₀ times the total charge enclosed in it (Φ = Q/𝜀₀).
Applications: Determining electric field intensity due to various charge distributions (e.g., hollow sphere, infinite sheet).
Current (I): Rate of flow of charge. I = Q/t. Unit: Ampere (A).
Ohm's Law: V = IR, provided physical state (temp) remains constant.
Resistivity (ρ): Resistance of a unit cube of material. R = ρL/A. Depends on temperature.
1st Rule (Current Law): Sum of currents meeting at a point is zero (ΣI = 0). Based on Conservation of Charge.
2nd Rule (Voltage Law): Algebraic sum of voltage changes in a closed loop is zero (ΣV = 0). Based on Conservation of Energy.
Wheatstone Bridge: Circuit used to measure unknown resistance. Balanced condition: R1/R2 = R3/R4 (No current in galvanometer).
Potentiometer: Instrument to measure potential difference accurately without drawing current. Uses null method. Used to compare EMFs of cells.