Calculadora de Campo Elétrico
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
E = k·q/r²
About this calculator
The Electric Field Calculator determines the intensity of the electric field generated by a point charge at a point in space. It uses Coulomb's law in field form, considering the electrostatic constant of vacuum (k = 8.99 × 10⁹ N·m²/C²), the charge value (q) in coulombs, and the distance (r) in meters to the point of interest. The result is given in newtons per coulomb (N/C) or volts per meter (V/m), indicating the force that would act on a unit positive test charge.
How it works: the formula E = k·q/r² shows that the field is directly proportional to the charge and inversely proportional to the square of the distance. For positive charges, the field is radially outward; for negative charges, radially inward. The calculator performs the calculation automatically; just enter the charge and distance values. It is not necessary to consider the test charge, as the field is a property of space generated by the source charge.
When to use: this tool is useful in electrostatics problems, such as calculating the field near an electron or proton, designing electronic devices, analyzing charge distributions in conductors, or in physics classes to check exercises. It is also applied in electrical engineering to estimate fields in high-voltage circuits or laboratory equipment.
Cautions: the formula is valid only for point charges and in vacuum. In material media, the dielectric constant alters the result. For very small distances (near the classical electron radius), quantum effects may invalidate the calculation. Remember to use consistent units: charge in coulombs and distance in meters. Avoid confusing electric field with electric potential, which is a different scalar quantity.
Frequently asked questions
What does the result in N/C mean?
Newtons per coulomb (N/C) is the unit of electric field, indicating the force (in newtons) that would act on a 1 coulomb test charge placed at the point.
Can I use the calculator for negative charges?
Yes, enter the charge value with a negative sign. The result will have the same magnitude, but the field direction will be radially inward (toward the charge).
Does the formula work for very large distances?
Yes, for distances much larger than the charge size, the point charge approximation is valid. The field decreases with the square of the distance.
What is the constant k and why is its value 8.99 × 10⁹?
k is Coulomb's constant, which depends on the medium. In vacuum, it is approximately 8.99 × 10⁹ N·m²/C². It relates the electric force to charges and distance.
What is the difference between electric field and electric potential?
Electric field is a vector quantity that measures force per unit charge; electric potential is scalar and measures potential energy per unit charge. They are related but different.