Editing Ground loop (electricity) (section)

===Sources of ground current===
The diagrams in this section show a typical ground loop caused by a signal cable ''S'' connecting two grounded electronic components ''C1'' and ''C2''.  The loop consists of the signal cable's ground conductor, which is connected through the components' metal chassis to the ground wires ''P'' in their power cords, which are plugged into outlet grounds which are connected through the building's utility ground wire system ''G''.

Such loops in the ground path can cause currents in signal cable grounds by two main mechanisms:
* [[Image:Ground loop - induced currents.svg|thumb|upright=1.2|Ground loop current induced by stray AC [[magnetic field]]s ''<span style="color:green;">(B, green)</span>'']] Ground loop currents can be induced by stray AC [[magnetic field]]s<ref name="Robinson" /><ref name="Vijayaraghavan8.8.3">
{{cite web
  | last = Vijayaraghavan | first = G.
  | author2=Mark Brown
  | author3=Malcolm Barnes
  | title = 8.8.3 Magnetic or inductive coupling
  | work = Electrical noise and mitigation - Part 3: Shielding and grounding (cont.), and filtering harmonics
  | publisher = EDN Network, UBM Tech
  | date = December 30, 2008
  | url = http://www.eetimes.com/document.asp?doc_id=1274126&page_number=3
  | access-date = March 24, 2014
}}</ref> ''<span style="color:green;">(B, green)</span>'' which are always present around AC electrical wiring.  The ground loop constitutes a conductive wire loop which may have a large area of several square meters.  According to [[Faraday's law of induction]], any time-varying [[magnetic flux]] passing through the loop induces an [[electromotive force]] (EMF) in the loop, causing a time varying current to flow.  The loop acts like a [[short circuit]]ed single-turn transformer winding; any AC [[magnetic flux]] from nearby transformers, electric motors, or just adjacent power wiring, will induce AC currents in the loop by induction.  In general, the larger the area spanned by the loop and the larger the magnetic flux through it, the larger the induced currents will be.   Since its [[Electrical resistance|resistance]] is typically very low, often less than 1 [[ohm]], the induced currents can be large.{{clear}}
* [[Image:Ground loop - leakage currents.svg|thumb|upright=1.6|Ground loop current caused by leakage currents in the building's ground wire system from an appliance ''A'']] Another less common source of ground loop currents, particularly in high-power equipment, is current leaking from the ''hot'' side of the power line into the ground system.<ref name="Vijayaraghavan8.11" /><ref name="Ballou2">This type is often called "common impedance coupling", [https://books.google.com/books?id=eh60Ue_K2QkC&pg=PA1198&dq=%22common+impedance+coupling   Ballou 2008 ''Handbook for Sound Engineers, 4th Ed.'', p. 1198-1200]</ref> In addition to resistive leakage, current can also be induced through low impedance capacitive or inductive coupling. The ground potential at different outlets may differ by as much as 10 to 20 volts<ref name="Whitlock" /> due to voltage drops from these currents. The diagram shows leakage current from an appliance such as an electric motor ''A'' flowing through the building's ground system ''G'' to the [[neutral wire]] at the utility ground bonding point at the [[electrical service panel|service panel]]. The ground loop between components ''C1'' and ''C2'' creates a second parallel path for the current.<ref name="Ballou2" /> The current divides, with some passing through component ''C1'', the signal cable ''S'' ground conductor, ''C2'' and back through the outlet into the ground system ''G''. The AC voltage drop across the cable's ground conductor from this current introduces hum or interference into component ''C2''.<ref name="Ballou2" />{{clear}}