Maxwell, however, considered that this law, standing alone, lacked symmetry; so he formulated the hypothesis that conversely a variable electric field should generate a magnetic one, and proceeded to construct his theory with this idea in view.[40] In the particular case of free space in which only fields but no charges or currents are present, Maxwell’s equations of electromagnetics, termed field-equations (since they describe the state of the electromagnetic field), can be written:
where
represents electric field intensity,
magnetic field intensity,
denotes time, and
