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CBSE Class 12-science Answered

What are the imp. conceptual questions from the chapter Alternating Current & EMI?
Is power factor at resonance is zero. How?
Asked by debjyotisaha98 | 19 Aug, 2015, 10:23: PM
answered-by-expert Expert Answer
Questions based on the follwoing concepts can be considered important:
 
1) Motional emf
2) Self and Mutual inductance
3) AC generator
 
4) AC applied to an inductor and a capacitor
5) Phasor diagram of AC applied to LCR circuit
6) Resonance and power in AC circuits
 
It is incorrect that power factor at resonance is zero. Infact power factor is maximum, i.e. equal to 1.
 
The power factor is defined as 
 
begin mathsize 14px style cosϕ equals straight R over straight Z equals fraction numerator straight R over denominator square root of straight R squared plus open parentheses straight X subscript straight L minus straight X subscript straight C close parentheses squared end root end fraction end style
 
At resonance, the capacitive and inductive reactance are same. So, we have
 
begin mathsize 14px style straight X subscript straight L minus straight X subscript straight C equals 0 therefore cosϕ equals fraction numerator straight R over denominator square root of straight R squared end root end fraction equals straight R over straight R equals 1 end style
Answered by Romal Bhansali | 20 Aug, 2015, 01:33: PM

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