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Methods of energy input

In a generał electromagnetic system we can identify the following methods of exchanging

energy between that system and its environment.

•    Moving charged bodies in an electric field. The forces on the charged bodies result in the performance of mechanical work.

•    Injecting currents from voltage sources into terminals of a network. It is usual to regard this as an example of the delivery of electrical power.

•    Moving polarised dielectrics in electric fields. The forces and torques on the polarised

bodies result in the performance of mechanical work.

•    Moving current carrying wires in a magnetic flux density. The forces on the wires require the performance of mechanical work. It is also true that the movement of the wires may cause changing magnetic fields which induce voltages in the circuits

in which the currents flow, causing an exchange of electric energy of a type described earlier.

•    Moving magnetised media in a magnetic field. The forces and torques exerted by the field on the poles of the media involve the performance of mechanical work. It is also true that changing fluxes caused by the movement may induce voltages in circuits which may be carrying currents to produce the magnetic field in which the motionistaking place.