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Cheat sheet · JEE Preparation Physics

Electrostatic Potential and Capacitance cheat sheet

The whole chapter on one page: key formulas, facts and the points to remember, for quick revision before a test.

JEE · Physics

Cheat sheet

Class 12 · Chapter 2Electrostatic Potential and Capacitance

Series capacitors add like parallel resistors (reciprocals).

1. Potential

V=kqrV = \dfrac{kq}{r}E=−dVdrE = -\dfrac{dV}{dr}
Vdipole=kpcos⁡θr2V_{dipole} = \dfrac{kp\cos\theta}{r^2}

Potential energy of two charges U=kq1q2rU = \dfrac{kq_1q_2}{r}. Equipotential surfaces are ⊥ to field lines.

2. Capacitors

C=QVC = \dfrac{Q}{V}C=ε0AdC = \dfrac{\varepsilon_0 A}{d}C=Kε0AdC = \dfrac{K\varepsilon_0A}{d} (dielectric)
1Cs=1C1+1C2\dfrac1{C_s} = \dfrac1{C_1} + \dfrac1{C_2}Cp=C1+C2C_p = C_1 + C_2
U=12CV2=Q22CU = \dfrac12CV^2 = \dfrac{Q^2}{2C}u=12ε0E2u = \dfrac12\varepsilon_0E^2

3. Conductors

  • E = 0 inside; charge resides on the surface.
  • Surface is equipotential.
  • Electrostatic shielding.

4. Key Points

  • Dielectric polarisation reduces field.
  • Work along equipotential = 0.
  • Unit of C: farad.
  • Sharing charge loses energy.

Remember: V = kq/r | C = ε₀A/d | series & parallel | U = ½CV²

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