If a test charge would experience a Coulomb force at a given point in space, then an electric field exists at that point. The field surrounding a source point charge of q coulombs at a distance of d metres from that charge is calculated by E=kq/d2. Here k is Coulomb's constant and the units of E are NC-1. The direction of an electric field is taken by convention to be the direction a positive charge would take if released into the field.
Fischer-Cripps. A.C., The Electronics Companion. Institute of Physics, 2005.
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