power in ac circuits

Thread Starter


Joined Jan 24, 2004
i want to know about the power in the ac circuits. i have got this one question which has been bugging me for quite some time :unsure: .if the source (as in domestic transformers) actually supplies a power(apparent) , only a fraction of which is actually available to the load(the real power), what actually happens to the remaining power supplied by the source (apparent power - real power). i am pretty sure that this value cannot be equal to the reactive power. i will be really grateful if someone could clear my doubt.


Joined Jan 22, 2004
:huh: hi,

you ask what happened to the remaining power, meaning if the load requires 1 ampere but the transformer is capable of giving out 3 amp, what happens to the remaining 2 amp.

ans. the amount of current that the transformer should produce depends upon current requirement of the load. if the load needs 1 ampere the transfo will give out 1 ampere not 3 ampere as what you are probably thinking. in other words, all current need of the secondary to which the load is connected will be supplied by the primary which is connected to the source.

without the load, current flowing at the primary is called magnetizing current and it maintains the self-induced voltage across the primary winding and compensates for the losses caused by the resistance of the wire used as well as the losses in the iron core. these losses are called eddy current losses and hysteresis losses. these losses causes the transfor to get warm during operation.

i hope this clears you up ;)