InterviewSolution
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InterviewSolution
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Define Power in AC circuits ? Derive an relation between true power & virtual power? |
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Answer» Solution :i. Power of a circuit is defined as the rate of consumption of electric energy in thate circuit. It is GIVEN by the PRODUCT of the voltage and current. In an vary continuously with time. ii. The alternating voltage and alternating current in the series RLC circuit at an instant are given by `v=V_(m)sinomegat" and "i=I_(m)sin(omegat+phi)` iii. where `phi` is the phase angle between v and i. The instantaneous power is then WRITTEN as `P=v_(i)` `=V_(m)I_(m)sinomegat[sinomegatcosphi-cosomegatsinphi)` `p=V_(m)I_(m)[cosphisin^(2)omegat-sinomegatsinphi]` iv. Here the average of `sinomegat" over a cycle is "(1)/(2)` and that of `sinomegatcosomegat` is zero. Substituting these values, we obtain average power over a cycle. `P_(av)=V_(m)I_(m)cosphixx(1)/(2)` `=(V_(m)I_(m))/(sqrt(2)sqrt(2))cosphi` `P_(av)=V_(RMS)I_(RMS)cosphi` v. where `V_(RMS)I_(RMS)` is called apparent power and `cosphi` is power FACTOR. The average power of an AC circuit is also KNOWN as the true power of the circuit. |
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