The question is: What happens if the fields are time varying? Or, perhaps, a better statement would be: How do we need to modify the fundamental postulates to treat time-varying electric and magnetic fields? Thischapterdiscussesthequestionoftimedependencyinsomedetail.Wewillseethattheelectricandmagneticfieldsunder time-varying conditions are interdependent. A time-varying electric field generates a time-varying magnetic field and vice versa. Thus, the time-dependent magnetic flux density B (and therefore H) is dependent on the electric field intensity E (and thereforeonD).Theabovepostulateswillbemodifiedtoaccountforthisdependency.Sincenowwemusttreatboththeelectric