When if ever are electric and magnetic fields decouple When

When, if ever, are electric and magnetic fields decouple? When both partial derivative rho_v/partial derivative t = 0 and partial derivative J/partial derivative t = 0 When either partial derivative rho_v/partial derivative t = 0 and partial derivative J/partial derivative t = 0 When both partial derivative rho_v/partial derivative t notequalto 0 and partial derivative J/partial derivative t notequalto 0 When either partial derivative rho_v/partial derivative t notequalto 0 and partial derivative J/partial derivative t notequalto 0 Electric an magnetic fields are always coupled.

Solution

Electric and magnetic fields are coupled but in quasistatic condition time varying condition the fields are decoupled in which the condition are monitored as the function of low frequency operation. Such as electrical machine or electromagnetic relays.

Best option suited is d.