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A direct current circuit is an electrical circuit that consists of any combination of constant voltage sources, constant current sources, and resistors. In this case, the circuit voltages and currents are independent of time. A particular circuit voltage or current does not depend on the past value of any circuit voltage or current.
Alessandro Giuseppe Antonio Anastasio Volta (UK: / ˈ v ɒ l t ə /, US: / ˈ v oʊ l t ə /; Italian: [alesˈsandro ˈvɔlta]; 18 February 1745 – 5 March 1827) was an Italian physicist and chemist who was a pioneer of electricity and power, [1] [2] [3] and is credited as the inventor of the electric battery and the discoverer of methane.
The war of the currents was a series of events surrounding the introduction of competing electric power transmission systems in the late 1880s and early 1890s. It grew out of two lighting systems developed in the late 1870s and early 1880s; arc lamp street lighting running on high-voltage alternating current (AC), and large-scale low-voltage direct current (DC) indoor incandescent lighting ...
Streetcars created enormous demand for early electricity. This Siemens Tram from 1884 required 500 V direct current, which was typical. Much of early electricity was direct current, which could not easily be increased or decreased in voltage either for long-distance transmission or for sharing a common line to be used with multiple types of electric devices.
"Dynamo Electric Machine" (end view, partly section, U.S. patent 284,110) A dynamo is an electrical generator that creates direct current using a commutator.Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current ...
These terms refer to how the current varies in time. Direct current, as produced by example from a battery and required by most electronic devices, is a unidirectional flow from the positive part of a circuit to the negative. [46]: 11 If, as is most common, this flow is carried by electrons, they will be travelling in the opposite direction.
Electric current can be directly measured with a galvanometer, but this method involves breaking the electrical circuit, which is sometimes inconvenient. Current can also be measured without breaking the circuit by detecting the magnetic field associated with the current. Devices, at the circuit level, use various techniques to measure current:
Edison in 1861. Thomas Edison was born in 1847 in Milan, Ohio, but grew up in Port Huron, Michigan, after the family moved there in 1854. [8] He was the seventh and last child of Samuel Ogden Edison Jr. (1804–1896, born in Marshalltown, Nova Scotia) and Nancy Matthews Elliott (1810–1871, born in Chenango County, New York).