What is the formula for Electric Field of a Point Charge?

The Electric Field of a Point Charge formula is E = kₑ × q / r², where E—Electric field strength (V/m or N/C); q—Source charge (C); r—Distance from the charge (m); kₑ—Coulomb constant.

What does E mean in the Electric Field of a Point Charge formula?

E is Electric field strength (V/m or N/C).

Electric Field of a Point Charge

Q: How do you calculate Electric Field of a Point Charge?

Use the formula E = kₑ × q / r². The electric field around a point charge describes the force per unit charge that a test charge would feel at a given distance. Enter the values you know in the calculator above and it solves for the remaining variable.

E = k · q / r²

Calculator

Electric Field

Charge

Distance

Result

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Formula

E = kₑ × q / r²

Description

The electric field around a point charge describes the force per unit charge that a test charge would feel at a given distance. It points radially outward from a positive charge and falls off as the inverse square of distance. The field is the cause; the force on any charge placed in it (F = qE) is the effect. Electric fields determine breakdown, corona, and the operation of every field-effect device.

Variables

E — Electric field strength (V/m or N/C)
q — Source charge (C)
r — Distance from the charge (m)
kₑ — Coulomb constant

Practical Notes

Air breaks down at about 3×10⁶ V/m (3 kV/mm). Field strength sets clearance and creepage requirements and the maximum voltage a dielectric can withstand.

Related Concepts

All Fields & Electromagnetism formulas →

Coulomb’s Law Electric Field of a Point Charge Electric Potential of a Point Charge Gauss’s Law (Electric Flux) Lorentz Magnetic Force Force on a Current-Carrying Wire Force Between Parallel Wires Magnetic Field of a Straight Wire

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