Electric Field

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The concept of an electric field was introduced. It was stated that the electric field concept arose in an effort to explain action-at-a-distance forces.

All charged objects create an electric field that extends outward into the space that surrounds it.

This is a fancy way of saying that the only way we can tell if a field exists is to place a test charge at that spot and see if it feels a force. (In other words, it takes one to know one).

The animation below shows a stationary charge (Although we have no way of knowing it is charged until we bring in a test charge).

When a test charge is brought in, a force is present on that charge and so it shows evidence of a field being present.

The electric field at a given point is defined as the (vectorial) force that would be exerted on a stationary test particle of unit charge by electromagnetic forces (i.e. the Lorentz force).

A particle of charge would be subject to a force.

Its SI units are newtons per coulomb (N⋅C−1) or,

equivalently, volts per metre (V⋅m−1), which in terms of SI base units are kg⋅m⋅s−3⋅A−1.

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