<P> where Δφ is the potential difference between the plates and d is the distance separating the plates . The negative sign arises as positive charges repel, so a positive charge will experience a force away from the positively charged plate, in the opposite direction to that in which the voltage increases . In micro - and nano - applications, for instance in relation to semiconductors, a typical magnitude of an electric field is in the order of 7006100000000000000 ♠ 10 V ⋅ m, achieved by applying a voltage of the order of 1 volt between conductors spaced 1 μm apart . </P> <P> Electrodynamic fields are E-fields which do change with time, for instance when charges are in motion . </P> <P> The electric field cannot be described independently of the magnetic field in that case . If A is the magnetic vector potential, defined so that B = ∇ × A (\ displaystyle \ mathbf (B) = \ nabla \ times \ mathbf (A)), one can still define an electric potential Φ (\ displaystyle \ Phi) such that: </P> <Dl> <Dd> E = − ∇ Φ − ∂ A ∂ t (\ displaystyle \ mathbf (E) = - \ nabla \ Phi - (\ frac (\ partial \ mathbf (A)) (\ partial t))) </Dd> </Dl>

The definition of an electric field is based upon law