Question

When AC current flows in a circuit, energy is moved into the circuit during the positive half cycle and moved out of the circuit during the negative cycle. Is this statement true or false and provide an explanation

Answer 1

If circuit contains only pure inductive or capacitive elements or combination of both then phase difference between current and voltage is 90 degree.In this situation average power dissipation by the circuit-

  

This is because during half cycle of altenating current, energy flows from sorce to circuit while in second half cycle energy is returned by the elements so for complete cycle average power dissipation is zero.So given statement is true only for that circuit which are purely reactive without any ohmic element.

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If circuit contains also resistive element along with capacitive and inductive element then power is dissipated during each half cycle.Average value of power dissipated by the circuit is only due to resistance and its value is given by-

So if circuit has some ohmic element then given statement is false.