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Electric field strength calculator

A-level Fields and space

Electric field strength is the force per unit positive charge.

E = F / Q

This free calculator is for A-level physics. Choose the quantity you want to find, enter the other values with their units, and it shows the working in the layout used in exams, with the answer to the number of significant figures you choose. The values shown are an example. Change them to your own.

Quantity to find

EElectric field strength to find 5000 V/m

FForce

QCharge

Significant figures

Working

Write the equation
E = F / Q
Substitute the values
E = 0.002 ÷ (4 × 10⁻⁷)
Calculate
E = 5000 V/m
Give the answer to 3 significant figures
E = 5000 V/m

Worked example

Find E, the electric field strength. Given: force F = 0.00200 N; charge Q = 4.00 × 10⁻⁷ C.

Write the equation
E = F / Q
Substitute the values
E = 0.002 ÷ (4 × 10⁻⁷)
Calculate
E = 5000 V/m
Give the answer to 3 significant figures
E = 5000 V/m

Symbols and units

Symbol	Quantity	SI unit
E	Electric field strength	V/m
F	Force	N
Q	Charge	C

Electric field strength: rearranged

To find electric field strength: E = F / Q
To find force: F = E Q
To find charge: Q = F / E

Exam tip

The force on a negative charge is opposite to the field direction.

Common questions

What is the formula for electric field strength?

The equation is E = F / Q, where E is the electric field strength (V/m); F is the force (N); Q is the charge (C).

What units should I use for electric field strength?

In SI units: electric field strength in V/m, force in N, charge in C. The calculator also accepts common alternatives such as kilometres, grams or minutes, and converts them for you.

How do I rearrange E = F / Q?

Rearranging gives these forms: to find electric field strength: E = F / Q. to find force: F = E Q. to find charge: Q = F / E.

Practise electric field strength questions

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More fields and space equations: Coulomb’s law, Uniform electric field, Field of a point charge, Newton’s law of gravitation, Gravitational field strength, Gravitational potential, Orbital period, Escape velocity. See the full list on the a-level physics equation calculator page.