# Electrostatic Potential and Capacitance Notes | SwaVid Electrostatic Potential and Capacitance, NCERT Class 12 Physics: notes with key ideas, formulas, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-12/physics/chapter/electrostatic-potential-and-capacitance Source: https://www.swavid.com/cbse/class-12/physics/chapter/electrostatic-potential-and-capacitance # Electrostatic Potential and Capacitance ## Formulas and definitions ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 12 Physics on SwaVid ### Electrostatic potential and work done ### Equipotential surfaces ### Potential energy of a charge system ### Electrostatics of conductors and dielectrics ### Capacitors and capacitance ### Energy stored in a capacitor ### Next chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 12 › Physics › Electrostatic Potential and Capacitance Notes written by SwaVid from the NCERT textbook. Class 12 Physics, Chapter 2. Key ideas, formulas and common mistakes. CBSE prints 16 marks for Units I-II together, not for this chapter alone. Short answer. This chapter introduces electrostatic potential, potential energy, and the principles of capacitance. Students learn how electric energy is stored in fields and how capacitors behave individually and in combinations. Source: NCERT Physics Part I (Reprint 2026-27) , Chapter 2, Electrostatic Potential and Capacitance The electrostatic potential at a point is the work done by an external force in bringing a unit positive charge from infinity to that point without acceleration. Electrostatic force is conservative, so the work done depends only on the initial and final positions, not on the path taken. An equipotential surface is a surface with a constant value of potential at all points. No work is done in moving a test charge over an equipotential surface, and the electric field is always perpendicular to the surface at every point. The potential energy of a system of charges is the work done by external forces in assembling the configuration from infinite separation. For an electric dipole in an external field, potential energy is lowest when the dipole is aligned parallel to the field. Inside a conductor, the electrostatic field is zero and the potential is constant throughout its volume. Dielectrics are non-conducting substances that develop an opposing induced dipole moment when placed in an external electric field. A capacitor is a system of two conductors separated by an insulator, used to store charge and electrostatic energy. Capacitance depends on the geometric shape, size, separation of the conductors, and the medium between them. Charging a capacitor requires work against the opposing electric field between its plates. This work is stored as electrostatic potential energy in the electric field within the dielectric medium. Try each question first. Then tap it to see the answer. V = (1 / (4πε₀)) × (q / r) V = (9.0 × 10⁹ N m² C⁻²) × (4.0 × 10⁻⁷ C) / (0.09 m) V = 3600 / 0.09 = 4.0 × 10⁴ V 4.0 × 10⁴ V 1 / C = 1 / C₁ + 1 / C₂ 1 / C = 1 / 3.0 + 1 / 6.0 = 3 / 6.0 = 1 / 2.0 μF⁻¹ C = 2.0 μF 2.0 μF U = (1/2) C V² U = 0.5 × (10.0 × 10⁻⁶ F) × (50.0 V)² U = 0.5 × 10.0 × 10⁻⁶ × 2500 = 1.25 × 10⁻² J 1.25 × 10⁻² J Current Electricity . Electric Charges and Fields . The 14 chapters of Class 12 Physics . CBSE does not give marks to one chapter. It prints 16 marks for Units I-II together (Electrostatics; Current Electricity). Electrostatic Potential and Capacitance is part of that group. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Current Electricity. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Ch 2 NCERT book - 16 marks, Units I-II together - 3 quick checks - Using 1 / r² instead of 1 / r for electric potential . Electric field scales as 1 / r² for a point charge, but electrostatic potential scales as 1 / r. - Adding capacitances in series directly like resistors . Capacitors in series add reciprocally: 1 / C = 1 / C₁ + 1 / C₂. Direct addition applies only to parallel combinations. - Confusing signs in the potential energy of a dipole, U = - p · E . Remember that potential energy is minimum (-pE) when p and E are parallel (θ = 0°), and maximum (+pE) when antiparallel (θ = 180°). - Assuming electric potential must be zero if the electric field is zero . The electric field is the negative derivative of potential with distance. Inside a charged spherical shell, E = 0, but V is constant and non-zero. ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 12](https://www.swavid.com/cbse/class-12) - [Physics](https://www.swavid.com/cbse/class-12/physics/chapters) - [Start free →](https://www.swavid.com/signup) - [All 14 chapters](https://www.swavid.com/cbse/class-12/physics/chapters) - [NCERT Physics Part I (Reprint 2026-27)](https://ncert.nic.in/textbook.php?leph1=0-8) - [Open notes](https://www.swavid.com/cbse/class-12/physics/chapter/current-electricity) - [Open notes](https://www.swavid.com/cbse/class-12/physics/chapter/electric-charges-and-fields) - [Class 12 Physics](https://www.swavid.com/cbse/class-12/physics/chapters) - [Start free →](https://www.swavid.com/signup)