Alternating Current
In alternating current (AC) circuits, the electric current periodically changes direction. This type of current is commonly used in households and businesses to power various devices.

Key Points:
- The voltage and current in an AC circuit vary sinusoidally with time.
- The frequency of the AC current is measured in hertz (Hz) and determines how many cycles occur in one second.
- The root mean square (RMS) value of an AC waveform is used to calculate the equivalent DC value that would produce the same amount of power in a resistor.
- AC circuits consist of resistors, capacitors, and inductors that interact differently with the changing current.

AC Waveforms
AC waveforms can be represented graphically as sine waves. The amplitude of the waveform corresponds to the peak voltage or current, while the frequency determines how quickly the wave oscillates.

AC Circuit Components
- Resistors: Resistors in an AC circuit dissipate energy in the form of heat and have a constant resistance value.
- Capacitors: Capacitors store and release electrical energy, causing a phase shift between voltage and current in the circuit.
- Inductors: Inductors store energy in a magnetic field and exhibit a phase shift opposite to that of capacitors.

Impedance
Impedance is the total opposition to the flow of AC current in a circuit and is a combination of resistance, inductive reactance, and capacitive reactance. It is represented as a complex number and affects the flow of current in the circuit.
Understanding the principles of alternating current is essential for designing and analyzing electrical circuits in various applications.