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In figure 12 ( b ) we have assumed that V L is greater than V C which makes i lags behind V . If V C > V L then , i lead V
In this phasors diagram OA represent V R , AD represent V C and AC represent V L . So in this case as we have assumed that V L > V C , there resultant will be ( V L -V C ) represented by vector AD
Vector OB represent resultant of vectors V R and ( V L -V C ) and this vector OB is the resultant of all the three , which is equal to applied voltage V , thus
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is called impedance of the circuit From phasors diagram 12 ( b ), current i lag behind resultant voltage V by an phase angle given by ,
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From equation ( 20 ) three cases arises ( i ) When ωL > 1 / ωC then tanφ is positive i . e . φ is positive and voltage leads the current i ( ii ) When ωL < 1 / ωC , then tanφ is negative i . e . φ is negative and voltage lags behind the current i ( iii ) When ωL = 1 / ωC , then tanφ is zero i . e . φ is zero and voltage and current are in phase Again considering case ( iii ) where ωL = 1 / ωC , we have
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This is the case where X L = X C , the circuit is said to be in electric resonance where the impedance is purely resistive and