CONCEPTS

What is an electric field?

We explain what is an electric field? The history of its discovery, how its intensity is measured and what its formula is.

  1. What is an electric field?

An electric field is a physical field or region of space that interacts with an electric force . Its representation by means of a model describes the way in which different bodies and systems of an electrical nature interact with it.

In physical terms, it is a vector field in which a given electric charge (q) suffers the effects of an electric force (F) .

These electric fields may be a consequence of the presence of electric charges, or of variable magnetic fields , as demonstrated by the experiments of British scientists Michel Faraday and James C. Maxwell.

For that reason, electric fields, in contemporary physical perspectives, are considered alongside magnetic fields to form electromagnetic fields.

Thus, an electric field is that region of space that has been modified by the presence of an electric charge . If we introduce a different electric charge, it will experience a punctual and meaningful electric force. In this way, a positive electric charge will direct the electric field outward, and a negative electric charge will inward.

  1. History of the electric field

The concept of electric field was first proposed by Michel Faraday , arising from the need to explain the action of remote electric forces. This phenomenon was key in his demonstration of electromagnetic induction in 1831, thereby checking the links between magnetism and electricity .

A subsequent contribution to the electric field was that of James Maxwell, whose equations described multiple aspects of the electrical dynamics of these fields, especially in his Dynamic Theory of the Electromagnetic Field (1865).

  1. Electric Field Units

The electric fields are not directly measurable , with any type of device. But it is possible to observe its effect on a load located nearby (intensity). Newton / coulomb (N / C) are used for this.

  1. Electric Field Formula

The basic mathematical formulation of electric fields is

F = qE

Where F is the electric force acting on the electric charge q inserted in the field with an intensity E . Note that both F and E are vector magnitudes, endowed with meaning and direction.

From there, it is possible to advance mathematically by incorporating Coulomb’s Law, obtaining that E = F / q = 1 / 4πϵ 0 = (q i / r 2 ) .ȓ i , where ȓ i are the unit vectors that mark the direction of the line that joins each load q i with each load q.

  1. Intensity of the electric field

electric field intensity sense
The positive electric charge drives the electric field outward and the negative one inwards.

The intensity of the electric field is a vector magnitude that represents the electric force F acting on a given charge in a precise amount of Newton / Coulomb (N / C). This magnitude is usually referred to simply as “electric field”, because the field itself cannot be measured, but its effect on a given charge.

To calculate it, the formula F = qE is used , taking into account that if the charge is positive (q> 0), the electric force will have the same sign as the field and q will move in the same direction; while if the charge is negative (q <0), everything will happen the other way around.

  1. Example of electric field

A simple example of the calculation of the intensity of an electric field is:

If we introduce an electric charge of 5 × 10 -6 C in an electric field that acts with a force of 0.04 N, how strong is that field?

Applying the formula E = F / q, we have that E = 0m04 N / 5 × 10 -6 C = 8,000 N / C.

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