
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 rootmeansquare value respectively.


The supply voltage (A) and the circuit current (E)
will always have a phase difference. The
phase difference 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 pi/2. 

The p.d. across the inductor (D) leads the current
(E) by pi/2. 

.In other words, (C)
and (D) are always 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 yaxis 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) `phase difference = 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 large in magnitudes. 