An electric field is an elegant way of characterising the electrical environment of a system of charges. The electric field at any point in space around a system of charges represents the force a unit positive test charge would experience if placed at that point. The term field in physics generally refers to a quantity that is defined at every point in space and may vary from point to point. The electric field is a vector field since force is a vector quantity.
Following is the table explaining other related concepts of electric field:
Electric Field Physical Significance
Under Static Condition
Under the static condition, an electric field characterises the electrical environment surrounding a system of charges. It is defined at every point and varies from point to point.
Electromagnetic Non-Static Condition
Under this condition, the accelerated motion of the charge gives rise to electromagnetic waves that propagate with a speed c and impart a force on another charge. Time-dependent magnetic and electric fields are associated with the transport of energy.
The electric field is independent of the test charge and is a characteristic for a system of charge. The interaction between charges is electromagnetic in nature.
The true physical significance of electric field emerges when we deal with time-dependent electromagnetic phenomena. Consider two distant charges q1 and q2 in accelerated motion. The effect of motion of q1 on q2 doesn’t arise instantaneously. There will be a time difference between the effect and the cause. This time delay is accounted for by the electric field as follows: The accelerated motion of q1 gives rise to electromagnetic waves. These waves travel at a speed of c and reach the charge q2 and impart a force on it. This accounts for the time delay.
Although electric and magnetic fields can only be detected by their effects (forces) on charges, they are perceived as physical entities, not merely mathematical constructs. They possess an independent dynamics of their own, in other words, they evolve according to laws of their own. They also carry energy. Therefore, a source of time-dependent electromagnetic fields turned on momentarily and switched off, leaves back propagating electromagnetic fields carrying energy. The concept of field was first introduced by Faraday and is now one of the central concepts in physics.
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