The advantage of electrical energy over other energies is that it could be transmitted over a long distance without much loss and with high efficiency.The devices which convert electrical energy into other forms of energy is known as electromechanical devices and the process is known as electromechanical energy conversion.The conversion takes place through either electrical or magnetic medium surrounding the device.The electromechanical devices could be classified into three categories primary ,secondary and tertiary.Primary includes the continuous energy conversion elements such as motors,generators etc ie the linear and rotating electrical machines.The second category includes transducers which could work on with even very small input and the tertiary the force producing devices like electromagnets,solenoids,relays etc

Energy conversion principle

The energy conversion principle is one and same ie “energy can neither be created nor be destroyed but could be transformed from one form to another”.In the case of motors generators etc the input energy is not converted fully into the output some amount of energy is wasted for ohmic losses ie due to heating effects as well as friction.so in the case of motor

Total input energy = mechanical energy output + energy stored in magnetic field+ energy wasted for losses.

It is same for generator the difference is that the output energy is electrical and input mechanical.

So if we draw an energy flow diagram for motor it will look as shown below.

Energy flow diagram for motor

Energy flow diagram for a generator

The energy flow equation could be written as

∫d W_input = ∫d W _output + ∫d W _{magnetic field} +∫d W _heat

Due to inertia of mechanical parts usually the electromechanical devices are slow moving so we have to give a coupling field to vary the field slowly and hence the field is quasi static in nature.

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