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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