Electrostatics (Electric Charges and Fields, Potential): One-Page Formula Sheet

Electrostatics (Electric Charges and Fields, Potential) — formula sheet

Formulas

• F = kq₁q₂/r², k = 1/(4πε₀)
• Infinite line: E = λ/(2πε₀r); infinite sheet: σ/(2ε₀)
• Point charge: V = kq/r; dipole on axis: E = 2kp/r³
• Potential energy U = kq₁q₂/r

Key ideas

• Field lines start on + and end on − charges
• Gauss's law: flux = q_enclosed / ε₀
• Field inside a conductor is zero; charge sits on the surface
• E = −dV/dr

Traps to avoid

• Adding fields as scalars
• Using Gauss's law where there is no symmetry
• Forgetting that potential is a scalar and can be added directly

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