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Long-distance electromagnetic telegraph systems from 1820 onwards [a] used two or more wires to carry the signal and return currents. It was discovered by German scientist C.A. von Steinheil in 1836–1837, that the ground could be used as the return path to complete the circuit, making the return wire unnecessary. [2]
Battery-powering one or more of the circuits can avoid a ground loop, because the entire device may be disconnected from mains power. A hazardous technique sometimes used by amateurs is to break the third wire ground conductor P in one of the component's power cords, by removing the ground pin on the plug, or using a cheater plug. This creates ...
A pooled analysis found consistent evidence of an effect of ELF-MF on childhood leukaemia. [23] An assessment of the burden of disease potentially resulting from ELF MF exposure in Europe found that 1.5–2% of childhood leukaemia cases might be attributable to ELF MF, but uncertainties around causal mechanisms and models of dose-response were ...
Special wiring rules apply to wet or corrosive locations, [13] and to locations which present an explosion hazard. [14] Wiring materials for use in the United States must generally be made and tested to product standards set by NEMA and Underwriters Laboratories (UL) and must bear approval marks such as those set by UL.
Stray voltage is the occurrence of electrical potential between two objects that ideally should not have any voltage difference between them. Small voltages often exist between two grounded objects in separate locations by the normal current flow in the power system.
A farm in the mountains of Norway stands on the site of what was once a “large and powerful Viking farm” and has yielded a significant Viking treasure.
One example is a shielded cable, which has electromagnetic shielding in the form of a wire mesh surrounding an inner core conductor. The shielding impedes the escape of any signal from the core conductor, and also prevents signals from being added to the core conductor.
Cruz, 24, slashed .233/.285/.450 with 17 home runs, 54 RBIs and 10 stolen bases in 87 games last season. He finished sixth in NL Rookie of the Year voting and earned a regular spot in the Pirates ...