Does anybody know about AC/DC in engineering?

Answer 1

AC dominates in industrial use of electricity as explained in
http://www.greatachievements.org/?id=2992
DC is used industrially in electrolysis for electroplating, extracting aluminium from bauxite and in chlorine and caustic soda from brine. http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0031622.html

Answer 2

AC power is different from DC in that both the voltage and current swing in direction back and forth one cycle every 1/50 s making a sine wave. The terminals thus have no fixed positive and negative value but at any instant are one or the other. This means that AC systems are actually turned off twice in 1/50 s. (Moving a hand rapidly in fluorescent light gives a slight stroboscopic effect - the hand appears to jerk instead of move smoothly. This is directly attributable to the hand being illuminated, thus seen by the eyes, in flashes.)

Alternating Current is produced almost accidentally by the generators used by power companies. The generators have rotating magnets and as these swing north to south and back, AC is generated. Obviously they are designed to do it but DC machines do exist.

The "240" volts produced is a special averaging to give a pure DC equivalent. In actual fact, our power supply swings between +339 and -339 volts.

The advantage of AC over DC is that power transmission is simpler under AC, it can be changed in voltage relatively easily using transformers, and that higher power motors can be devised under AC. Disadvantages also exist such as energy loss in radiation and in eddy currents generated in nearby metals. Further problems can exist when the swings of voltage and current get out of time with each other.

Answer 3

Oh, that kind of AC/DC... AC stands for Alternating Current, which means that the current changes its direction of flow in a sinusoidal pattern caused by the the generator that's making it. AC is typically generated in the US at 60 Hertz in three phases that are 120 degrees apart. It's often 50 Hertz elsewhere in the world. DC is direct current, which means that the current is always flowing in one direction. A battery is a source of DC. DC, like AC, can be generated, but losses are much greater trying to distribute it over long distances. AC can be turned into DC by passing it through a rectifier, such as a diode. Passing AC through a single diode results in half of the sine wave, and thus, half of the available power, being lost. This is known as half-wave rectification. A full-wave rectifier can be made with four diodes in a "bridge" configuration, or by using two diodes and a center-tapped transformer. A full-wave rectifier flips the negative half of the sine wave to positive, and thus, its output pulses at twice the rate of its input, and the power lost is almost nothing. Electronic inverters can be used convert DC into AC, usually with a process known as pulse width modulation, or PWM. The speed of an AC motor is dependent upon the frequency of the AC being applied, not the level of the voltage, so PWM is often used in variable speed AC motor drives.

Answer 4

In electrical engineering , AC is Alternate Current and DC is Direct Current.