Formulas & tables/Physics/Electrostatics/Electric field strength

Electric field strength

E=FqE=\dfrac{F}{q}

Result unit: V/m (= N/C)

What it describes

The electric field strength is the force acting on a unit test charge.

Symbols

EE
field strength
[V/m]
FF
force
[N]
qq
test charge
[C]

Where it comes from

Field strength describes how strongly the field would act on a unit test charge at a given point — regardless of whether that charge is actually there.

When to use it

Describing an electric field; the force on a charge is F=qEF=qE.

Example

A field acts on a charge of 2⋅10−62\cdot10^{-6} C with a force of 0.4 N. Calculate the field strength.
SubstitutionF=0.4F=0.4 N, q=2⋅10−6q=2\cdot10^{-6} C.
ResultE=0.42⋅10−6=2⋅105E=\dfrac{0.4}{2\cdot10^{-6}}=2\cdot10^{5} V/m.

Related formulas

Coulomb's law Voltage / work done by the field

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