PhysRefPhysics reference
Electricity & Magnetism
E=Fq=kQr2E = \frac{F}{q} = k\frac{Q}{r^2}

Electric field is force per unit charge.

Variables

E
Electric field
Field strength
N/C
F
Force
Force on test charge
N
q
Test charge
Small positive charge
C
Q
Source charge
Field-creating charge
C
r
Distance
From source
m

Derivation

E = F/q by definition. For point charge: E = kQ/r².

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Common questions

What is the Electric Field formula?

Electric Field is written E = F/q = kQ/r². Electric field is force per unit charge. It belongs to Electricity & Magnetism, under Electrostatics.

What are the units in E = F/q = kQ/r²?

In SI units, E is electric field, measured in kg·m/(A·s³); F is force, measured in kg·m/s²; q is test charge, measured in A·s; Q is source charge, measured in A·s; r is distance, measured in m.

How is the Electric Field formula derived?

E = F/q by definition. For point charge: E = kQ/r². The result is E = F/q = kQ/r².