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Electrostatics II: Potential & Capacitance formula sheet

Every formula in the Electrostatics II: Potential & Capacitance chapter for JEE Main, with one line on when it applies. Topic 1 is open to everyone; sign in free to read all 29 and download the PDF.

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How we count: 7× asked means 7 past JEE Main questions in the PrepWiser bank needed that formula, and "last" is the latest year one appeared. ★ marks formulas asked 8 or more times.

Electric potential

Potential of point charges
6× asked, last 2025
V=14πε0∑iqiri,VA−VB=∫ABE⃗⋅dl⃗V=\frac1{4\pi\varepsilon_0}\sum_i\frac{q_i}{r_i},\qquad V_A-V_B=\int_A^B\vec E\cdot d\vec l
Scalar: add with signs. Zero at infinity; volt = J/C.
Ring and disc on the axis
3× asked, last 2024
Vring=kQR2+x2,Vdisc=σ2ε0(R2+x2−x)V_{\text{ring}}=\frac{kQ}{\sqrt{R^2+x^2}},\qquad V_{\text{disc}}=\frac\sigma{2\varepsilon_0}\left(\sqrt{R^2+x^2}-x\right)
Centre of any ring or arc: kQ/RkQ/R. Half ring: λ/4ε0\lambda/4\varepsilon_0, independent of RR.
Shell or conducting sphere
7× asked, last 2025
V=kQR (r≤R),V=kQr (r≥R)V=\frac{kQ}R\ (r\le R),\qquad V=\frac{kQ}r\ (r\ge R)
Flat inside, not zero. Concentric shells: use the larger of shell radius and point distance.
Uniformly charged solid sphere
Vin=kQ(3R2−r2)2R3,Vcentre=1.5 kQRV_{\text{in}}=\frac{kQ(3R^2-r^2)}{2R^3},\qquad V_{\text{centre}}=1.5\,\frac{kQ}R
Insulating sphere; parabola inside, kQ/rkQ/r outside.
Dipole potential
3× asked, last 2025
V=kpcos⁡θr2,Vaxial=kpr2,Veq=0V=\frac{kp\cos\theta}{r^2},\qquad V_{\text{axial}}=\frac{kp}{r^2},\qquad V_{\text{eq}}=0
Short dipole. V=0V=0 on the equator but E=kp/r3E=kp/r^3 there.
Infinite line and sheet
1× asked, last 2025
V1−V2=2kλln⁡r2r1,V1−V2=σ2ε0(x2−x1)V_1-V_2=2k\lambda\ln\frac{r_2}{r_1},\qquad V_1-V_2=\frac\sigma{2\varepsilon_0}(x_2-x_1)
Only differences are defined.

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Practise Electrostatics II: Potential & Capacitance

23 more formulas in 5 topics

Field, equipotentials and energy; Conductors and capacitance; Combinations and circuits; Energy and charge sharing; and Dielectrics. Read the first part free. Sign in free with Google to read the rest and download the PDF.

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Field, equipotentials and energy

  • Field from potential3×
  • Equipotential surfaces4×
  • Potential energy of a system3×
  • Work and energy conservation6×
  • Dipole in a uniform field4×

Conductors and capacitance

  • Connected spheres6×
  • Merging drops5×
  • Capacitance7×
  • Spherical and cylindrical capacitors
  • Parallel plate capacitor8×
  • Force between the plates2×

Combinations and circuits

  • Series and parallel12×
  • Balanced bridge9×
  • Capacitor in a DC circuit21×
  • RC charging and discharging

Energy and charge sharing

  • Energy stored8×
  • Energy density2×
  • Work done by the battery2×
  • Charge sharing18×

Dielectrics

  • Dielectric9×
  • Slab of thickness tt13×
  • Dielectrics in series and parallel17×
  • Inserting a dielectric11×

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About 170 past JEE Main questions from this chapter, with instant answer checking and step-by-step solutions where available. Free, and you can start without signing up.

Practise Electrostatics II: Potential & Capacitance

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