Electric Field Calculator

Compute electric field from a point charge: E = kQ/r², or from force/charge: E = F/q.

Inputs

Result

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General calculation reads

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How to use this calculator

  • Pick the mode.
  • Enter charge in Coulombs (or force in N) and distance in meters (or test charge in C).
  • Read field magnitude.

About this calculator

Electric field describes the force per unit charge that a test particle would feel. From a point charge: E = kQ/r² where k = 8.988×10⁹ N·m²/C². Field has units of N/C (equivalently V/m). Point inward from a negative charge, outward from positive.

Frequently asked

What is Coulomb's constant?+
k = 8.988 × 10⁹ N·m²/C² (or 1/(4πε₀)). Sometimes called the electrostatic constant.
How is field different from potential?+
Field E is force per charge (N/C). Potential V is energy per charge (J/C = V). E = -dV/dx (field = negative gradient of potential).
Is the field inside a conductor zero?+
In electrostatic equilibrium, yes — charges arrange themselves on the surface so the interior field cancels.
What is 1 V/m physically?+
A potential difference of 1 volt across 1 meter — a very weak field. Earth's natural fair-weather field is ~100 V/m.
Why does the formula use 1/r²?+
Because field lines spread over the surface of a sphere, whose area grows as 4πr². The field strength is proportional to 1/r² as a result.

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C = Q/V or parallel-plate C = ε₀A/d. Compute capacitance, charge stored, or energy.
Electrical Power Calculator
P = IV — compute power from voltage and current, or from voltage and resistance, or current and resistance.
Inductance Calculator
L = μ₀N²A/ℓ for an ideal solenoid, or V = L(dI/dt) for the defining equation.
RC Time Constant Calculator
τ = RC. Time for an RC circuit to charge to ~63% (or discharge to ~37%) of final value.
Wavelength ↔ Frequency Calculator
c = λ × ν. Wavelength in vacuum from frequency or vice versa. c = 3×10⁸ m/s.

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