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Electrostatics I: Charges, Field & Gauss's Law formula sheet

Every formula in the Electrostatics I: Charges, Field & Gauss's Law chapter for JEE Main, with one line on when it applies. Topic 1 is open to everyone; sign in free to read all 35 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.

Charge and Coulomb's law

Coulomb's law
23× asked, last 2025
F=14πε0K q1q2r2F=\frac1{4\pi\varepsilon_0K}\,\frac{q_1q_2}{r^2}
1/4πε0=9×1091/4\pi\varepsilon_0=9\times10^9 N m2^2C−2^{-2}. Medium: divide by KK. Fe/FgF_e/F_g (e–p) ≈ 103910^{39}.
Vector form
1× asked, last 2026
F⃗on 2=q1q24πε0 r⃗2−r⃗1∣r⃗2−r⃗1∣3\vec F_{\text{on }2}=\frac{q_1q_2}{4\pi\varepsilon_0}\,\frac{\vec r_2-\vec r_1}{|\vec r_2-\vec r_1|^3}
Divide by r3r^3; signs of qq fix the direction.
Splitting a charge
F∝q(Q−q) ⇒ q=Q2 for Fmax⁡F\propto q(Q-q)\ \Rightarrow\ q=\frac Q2\ \text{for}\ F_{\max}
Fixed distance.
Quantisation of charge
3× asked, last 2026
q=±ne,e=1.6×10−19 Cq=\pm ne,\qquad e=1.6\times10^{-19}\ \text{C}
Additive and conserved. Body at +q+q has lost q/eq/e electrons.
Sharing on contact
4× asked, last 2025
q1′=q2′=q1+q22q_1'=q_2'=\frac{q_1+q_2}2
Identical conductors, signs included; update after each touch.
Two hanging charged balls
4× asked, last 2024
tan⁡θ=Femg,x3=q2l2πε0mg\tan\theta=\frac{F_e}{mg},\qquad x^3=\frac{q^2l}{2\pi\varepsilon_0mg}
Small θ\theta. Same angle in a liquid if K=ρ/(ρ−ρl)K=\rho/(\rho-\rho_l).

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Practise Electrostatics I: Charges, Field & Gauss's Law

29 more formulas in 4 topics

Electric field, Charge distributions and conductors, Electric dipole and Flux and Gauss's law. Read the first part free. Sign in free with Google to read the rest and download the PDF.

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Electric field

  • Field of point charges13×
  • Continuous charge
  • Null point of two charges5×
  • Three charges in equilibrium
  • Charged bob in a field11×
  • Charge across a uniform field8×

Charge distributions and conductors

  • Infinite line charge8×
  • Finite rod2×
  • Point on the rod's line2×
  • Ring on its axis4×
  • Arc at its centre3×
  • Disc on its axis1×
  • Sheet and conductor surface15×
  • Spherical shell or conductor10×
  • Uniformly charged solid sphere5×
  • Long charged cylinder2×
  • Conductors joined by a wire8×

Electric dipole

  • Dipole moment1×
  • Short dipole: axial, equatorial7×
  • Short dipole: any point
  • Exact axial field6×
  • Dipole in a uniform field10×
  • Work to rotate; oscillations
  • Dipole in a non-uniform field2×

Flux and Gauss's law

  • Flux12×
  • Flux through a disc
  • Gauss's law28×
  • Charge and a cube8×
  • Field lines2×

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About 150 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 I: Charges, Field & Gauss's Law

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