RCL a.c. series circuit

	The small square at the left of each waveform shows the variation of its instantaneous value.


	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.
	G) shows three rotating vectors (phasors), their projections on the y-axis corresponds to the three instantaneous voltages.
	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 .