Electric Field Calculator

The Electric Field Calculator finds the strength of the electric field produced by a point charge at a given distance — a fundamental concept in physics and electrical engineering. Enter the Charge (Q) in microcoulombs, the Distance (r) from the charge, and the Relative Permittivity (εr) of the surrounding medium to calculate the Electric Field (E) in N/C. Secondary outputs include the field in scientific notation, the charge converted to Coulombs, and the effective Coulomb's constant adjusted for your chosen medium.

μC

Enter the magnitude of the point charge in microcoulombs (μC).

m

Distance from the point charge to the observation point in meters.

Relative permittivity of the medium. Use 1 for vacuum or air, ~80 for water.

Results

Electric Field (E)

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Electric Field (Scientific Notation)

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Charge in Coulombs

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Effective Coulomb's Constant (k/εr)

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Results Table

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Frequently Asked Questions

What is an electric field?

An electric field is a region of space where a charged particle experiences a force. It is generated by electric charges and described as the force per unit charge at any given point. Every point charge creates its own electric field that radiates outward (for positive charges) or inward (for negative charges).

How do I find the electric field of a point charge?

The electric field E due to a point charge Q at a distance r is given by E = kQ / r², where k is Coulomb's constant (approximately 8.99 × 10⁹ N·m²/C²). If the medium is not a vacuum, divide k by the relative permittivity εr of the medium. The result is in Newtons per Coulomb (N/C).

What is the SI unit of electric field?

The SI unit of electric field is Newtons per Coulomb (N/C), which is equivalent to Volts per meter (V/m). Both units are used interchangeably in physics and engineering.

Is electric field intensity a scalar or a vector quantity?

Electric field intensity is a vector quantity — it has both magnitude and direction. The direction points away from positive charges and toward negative charges. This calculator computes the magnitude of the electric field.

How does the electric field vary with distance for a point charge?

The electric field follows an inverse-square law: it decreases proportionally to 1/r². This means if you double the distance from a point charge, the electric field drops to one-quarter of its original value. The field weakens rapidly as you move farther away.

What is the difference between electric field and electric force?

The electric field E is the force per unit charge (E = F/q). The electric force F on a specific charge q in the field is then F = qE. The electric field is a property of space created by source charges, while the force depends on both the field and the test charge placed in it.

Why is the electric field inside a conductor zero?

In electrostatic equilibrium, free electrons in a conductor redistribute themselves until the net internal electric field is zero. Any external field causes charge movement until the opposing internal field exactly cancels it. This is why conductors shield their interiors from external electric fields.

How does relative permittivity affect the electric field?

Relative permittivity (εr), also called the dielectric constant, reduces the effective Coulomb's constant in a medium. The modified formula becomes E = kQ / (εr · r²). For example, water has εr ≈ 80, so the electric field in water is about 80 times weaker than in vacuum for the same charge and distance.