The current or e.m.f., whose magnitude changes with time and direction reverses periodically is known as alternating current or e.m.f. This note provides us an information about alternating circuits.

Alternating current is positive during the first half cycle and negative during another half cycle, so the mean average value of a.c. over one cycle is zero. This note provides us an information on the mean value of alternating current.

Root Mean Square value of AC is that steady current when passed through a resistance for a given time produces the same amount of heat as the alternating current does in the same resistance in the same time. This note provides us an information on root mean square value of AC and AC through a resistance only.

An alternative e.m.f applied to an ideal inductor of inductance L. Such circuit is known as a purely inductive circuit. This note provides us an information on inductive and capacitive reactance.

The effective opposition of L-R circuit to a.c. called impedance of LR circuit. This note provides us an information on A.C. through an inductance and resistance and A.C. through capacitance and resistance.

The total effective opposition offered by LCR circuit to alternating current is known as impedance. This note provides us an information on A.C. through an inductance, capacitance and resistance.

Electrical resonance is said to take place in a series LCR circuit when the circuit allows maximum current for a given frequency of the source of alternating supply for which capacitive reactance becomes equal to the inductive reactance. This note provides us an information on electrical resonance in series LCR circuit and quality factor.

The average power over a complete cycle in an inductive circuit is the product of virtual e.m.f., virtual current and cosine of the phase angle between the voltage and the current. This note provides us an information on power consumed in a peries LCR circuit.