RCL series a.c. circuit
| The small square at the left of each waveform shows the instantaneous value. | |
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| The subscripts "o" and "rms" stand for peak value and root-mean-square value respectively. | |
| The supply voltage (A) and the circuit current (E) will always have a phase difference, f. The value of f can be found by using the triangle (H). If the inductive reactance is greater than the capacitive reactance, the supply voltage will lead the current; if the inductive reactance is smaller than the capacitive reactance, the supply voltage will lag behind the current . | |
| The p.d. across the resistor (B) oscillates inphase with the current (E). | |
| The p.d. across the capacitor (C) lags behind the current (E) by p/2. | |
| The p.d. across the inductor (D) leads the current (E) by p/2. | |
| .In other words, (C) and (D) are wlays in antiphase. | |
| The four RMS volatges are related by the triangle (H). | |
| The curve (F) shows the variation of the reciprocal of the impedance against frequency. | |
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G) shows three rotating vectors (phasors), their projections on the y-axis corresponds to the three instantaneous voltages. |
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| Series resonance is achieved by adjusting f, L or C such that the black dot is exactly at the highest point of the curve (F). | |
| At resonance, (i) f = 0 and (ii) Z = R. Therefore, (A) and (B) become exactly identical, (A) and (E) are inphase. The circuit current (E) is the greatest. | |
| At resonance, the p.d. across the capacitor (C) and that across the inductor (D) may be very large . |
