In
electrical engineering, a node is any region on a circuit between two
circuit elements. In
circuit diagrams, connections are ideal wires with zero resistance, so a node consists of the entire section of wire between elements, not just a single point.
According to
Ohm's law
Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance, one arrives at the usual mathematical equatio ...
, ''V = IR'', the voltage across any two points of a node with negligible resistance is
:
showing that the
electric potential
The electric potential (also called the ''electric field potential'', potential drop, the electrostatic potential) is defined as the amount of work energy needed to move a unit of electric charge from a reference point to the specific point in ...
at every point of a node is the same.
There are some notable exceptions where the voltage difference is large enough to become significant:
* High-precision resistance measurements using a
Kelvin connection
Four-terminal sensing (4T sensing), 4-wire sensing, or 4-point probes method is an electrical impedance measuring technique that uses separate pairs of current-carrying and voltage-sensing electrodes to make more accurate measurements than the s ...
* The difference in voltage between
ground and neutral
Ground and neutral are circuit conductors used in alternating current electrical systems. The ground circuit is connected to earth, and neutral circuit is usually connected to ground. As the neutral point of an electrical supply system is often ...
, between the
neutral wire
Ground and neutral are circuit conductors used in alternating current electrical systems. The ground circuit is connected to earth, and neutral circuit is usually connected to ground. As the neutral point of an electrical supply system is often ...
and the
ground in
domestic AC power plugs and sockets
AC power plugs and sockets connect electric equipment to the alternating current (AC) mains electricity power supply in buildings and at other sites. Electrical plugs and sockets differ from one another in voltage and current rating, shape, ...
, can be fatal. A properly installed electrical system connects them together at only one location, leading many people to the fatally incorrect conclusion that they are at "the same" voltage, or that the safety ground is "redundant and unnecessary"
* The
Seebeck effect
The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when ...
and the
Peltier effect
The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when ...
* Joints involving
aluminium wire
Dots used to mark nodes on a circuit diagram are sometimes referred to as ''meatballs''.
[Mansfield, Michael; O'Sullivan, Colm (2010), ''Understanding Physics (2nd edition)'', Chapter 14, page 359, John Wiley & Sons]
References
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Electricity