Coulomb's law for the force b/w charges encourages us to think in term of action at a distance represented as
Again introducing the field as an intermediary b/w the charges, we can represent the interaction as
Therefore the first charge sets up an electric field, the second charge interact with the electric field of the first charge. Our problem of determining the interaction b/w the charges is therefore reduced to two separate problems >>(1) determine, by measurement or calculation, the electric field established by the first charge at every point in space, and >> (2) calculate the force that the field exerts on the second charge placed at a particular point in space. In analogy with the following equation
for the gravitational field, we define the electric field E associated with a certain collection of charges in term of the force exerted on a positive test charge Q. at a particular point, or
The direction of vector E is the same as the direction of F, because q. is a positive scalar.
Dimensionally: The electric field is the force per unit charge.
SI Unit: Newton / Coulomb
( N/C)
Equivalent Unit: Volt/meter (V/m)
In gravitational field, g is usually expressed in units of m/s^2 and it can also be expressed as the force per unit mass in units of Newton/kilogram. Both the gravitational and electric field can be expressed as a force divided by a property ( mass or charge ) of the test body
Table of Some Electric Field
Note: Approximate Values
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