Consumer voltages vary somewhat depending on the country and size of load, but generally motors and lighting are built to use up to a few hundred volts between phases. Near the loads, the transmission voltage is stepped down to the voltages used by equipment. In a power plant, energy is generated at a convenient voltage for the design of a generator, and then stepped up to a high voltage for transmission. High voltages have disadvantages, such as the increased insulation required, and generally increased difficulty in their safe handling.

The lines in the picture are located in eastern Utah. Three-phase high voltage transmission lines use alternating currents to distribute power over long distances between electric generation plants and consumers. Power is often transmitted at hundreds of kilovolts on pylons, and transformed down to tens of kilovolts to be transmitted on lower level lines, and finally transformed down to 100В V вЂ“ 240В V for domestic use. The power losses ( P w Д¬onsequently, power transmitted at a higher voltage requires less loss-producing current than for the same power at a lower voltage. Use of a higher voltage leads to significantly more efficient transmission of power. This allows the power to be transmitted through power lines efficiently at high voltage, which reduces the energy lost as heat due to resistance of the wire, and transformed to a lower, safer, voltage for use. From left to right: G=generator, U=step up transformer, V=voltage at beginning of transmission line, Pt=power entering transmission line, I=current in wires, R=total resistance in wires, Pw=power lost in transmission line, Pe=power reaching the end of the transmission line, D=step down transformer, C=consumers.Д®lectrical energy is distributed as alternating current because AC voltage may be increased or decreased with a transformer.

These currents typically alternate at higher frequencies than those used in power transmission.ДЄ schematic representation of long distance electric power transmission. These types of alternating current carry information such as sound (audio) or images (video) sometimes carried by modulation of an AC carrier signal. Audio and radio signals carried on electrical wires are also examples of alternating current. In certain applications, like guitar amplifiers, different waveforms are used, such as triangular waves or square waves.

The usual waveform of alternating current in most electric power circuits is a sine wave, whose positive half-period corresponds with positive direction of the current and vice versa.

The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage. A common source of DC power is a battery cell in a flashlight. Alternating current is the form in which electric power is delivered to businesses and residences, and it is the form of electrical energy that consumers typically use when they plug kitchen appliances, televisions, fans and electric lamps into a wall socket. Alternating current ( AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction.

Sumber arus listrik ac dan dc