Fields Varying in Time
John E. Parton, S. J. T. Owen · 1975
Previously our discussion has been concerned with steady or static charges and steady or direct currents. The fields were electrostatic and magnetostatic. Now we study the effects of time variations of charges, currents and potentials. Of particular interest will be fields arising from sinusoidal variations at both low and high frequency. The effect of varying fields, in time, on Maxwell’s equations will be to leave the divergence equations unaltered but to modify the curl equations. This modification is due to (i) the electric field E produced by a changing magnetic field B which derives from Faraday’s experimental law and (ii) an inspired hypothesis of Maxwell which modifies Ampère’s circuital law to include the time variation of the electric flux density.