What is Direct Current ?

an attempt to show that AC was more dangerous than DC. In attempt to display these dangers, Harold P. Brown and Arthur Kennelly, employees of Edison, designed the first electric chair for the state of New York using AC.

To maintain the power at a constant level, most equipment uses rechargeable batteries so that the charge can be replenished regularly.

n 1891, the International Electro-Technical Exhibition was held in Frankfurt, Germany and displayed the first long distance

DC systems of the day. DC is the European standard.Many of DC's deficiencies were later corrected

The charger consists of a rectifier circuit which converts the readily available AC into a suitable DC voltage

transmission of three-phase AC, which powered lights and motors at the exhibition. Several representatives from what would

Other than changing the mains AC to DC

General Electric were present and were subsequently impressed by the display. The following year, General Electric formed and began to invest in AC technology.

Westinghouse won a contract in 1893 to build a hydroelectric dam to harness the power of Niagara falls and transmit AC to Buffalo

most power supplies change the level of the voltage.

The project was completed on November 16, 1896 and AC power began to power industries in Buffalo. This milestone marked the decline of DC in the United States.

but not until a substantial North American infrastructure had already been developed.

the voltage since most of the electronics functions

Usually represented as two wires leading to a device that uses electricity, electric power distribution requires a circuit

. While Europe would adopt an AC standard of 220-240 volts at 50 Hz, the standard in North America would become 120 volts at 60 Hz.

Swiss engineer René Thury used a series of motor-generators to create a high-voltage DC system in the 1880s,

Sources of direct Current

One wire is negative and the other is either is positive or neutral (ground) in AC current

which could be used to transmit DC power over long distances. However, due to the high cost and maintenance of the Thury systems, HVDC was never adopted for almost a century.

With the invention of semiconductor electronics in the 1970s, economically transforming between AC and DC became possible.

Most equipment are more efficient when directly powered from DC

The two wires take turns at sending electricity.

Less risks of shock hazard for voltages below 48 Volts

Specialized equipment could be used to generate high voltage DC power (some reaching 800 kV). Parts of Europe have begun to employ HVDC lines to electrically connect various countries.

HVDC lines experience less loss than equivalent AC lines over extremely long distances.