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What is Electric Field Strength?

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Electric field strength is defined at a point in the field as being equal to the force that would be exerted on a small unit charge (one coulomb) placed at that point. Electric field strength is also known as electric field intensity and is an expression of the intensity of an electric field at a particular location.

The idea of an electric field was first proposed by Michael Faraday and is produced by any electrically charged object. Other charged objects in the vicinity of the first object are affected by this field. The direction of the force gives the direction of the electric field. Electrical energy is contained in the electric fields and is proportional to the square of the field strength. Electric field strength is a vector quantity (it has both magnitude and direction). A moving electric charge produces a magnetic field, and in fact the two types of field are interrelated, and can be regarded as the same phenomenon viewed from different frames of reference.

The SI unit of electric field strength is newtons per coulomb (N/C) or volts per meter (V/m).

Coulomb's law states that the force acting between two charges is proportional to the product of the charges and inversely proportional to the distance between them squared. In mathematical terms:

F = k q1 q2 / r2

Where q1 and q2 are two point charges, F is the force that acts on each of the two point charges, r is the distance between the charges and k is the constant of proportionality. The value of k depends on the medium between the two charges. If the two charges are separated by free space, then k=1 / (4 π)

The force experienced by a very small test charge q placed in a field E in a vacuum is given by E = F/q, where F is the force experienced. The test charge q has to be infinitesimal so that it does not distort the field being measured.

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