AC is the standard form of electric power delivered to businesses and residences. It is also the type of electrical energy used when people plug their kitchen appliances, televisions, fans, and electric lamps into a wall socket. Batteries in flashlights are a common source of DC power.
Electric current can either be direct current (DC) which flows in one direction, or alternating current (AC), which periodically reverses direction and changes its magnitude continuously with time.
The abbreviations AC and DC often refer to alternating and direct current, respectively. In most electric power circuits, the alternating current waveform is a sine wave. This waveform’s positive half-period corresponds with the positive direction of the present and vice versa. However, different waveforms, like triangular or square waves, are used for specific applications like guitar amplifiers.
Alternating currents also carry information in the form of audio and radio signals on electrical wires. These signals are carried by modulation of an AC carrier signal, including sound (audio) or images (video). These alternating currents typically alternate at higher frequencies than those used in power transmission.