electrical engineering Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems that use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the l ...

, a node is any region or joining point on a circuit between two

circuit elements Circuit may refer to: Science and technology Electrical engineering * Electrical circuit, a complete electrical network with a closed-loop giving a return path for current ** Analog circuit, uses continuous signal levels ** Balanced circui ...

. In

circuit diagram A circuit diagram (or: wiring diagram, electrical diagram, elementary diagram, electronic schematic) is a graphical representation of an Electrical network, electrical circuit. A pictorial circuit diagram uses simple images of components, whil ...

s, connections are ideal

wire file:Sample cross-section of high tension power (pylon) line.jpg, Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample d ...

s with zero resistance. Whether "node" refers to a single point of junction or an entire equipotential region varies by the source. "Node" is often used, especially in

mesh analysis Mesh analysis (or the mesh current method) is a circuit analysis method for Planar graph, planar circuits; planar circuits are circuits that can be drawn on a Plane (mathematics), plane surface with no wires crossing each other. A more general ...

, to mean a principal node, which is distinct from the usage defined above. A principal node is a point in a circuit diagram where three or more connections meet. Principal nodes are important points of consideration in applying

Kirchhoff's circuit laws Kirchhoff's circuit laws are two equalities that deal with the current and potential difference (commonly known as voltage) in the lumped element model of electrical circuits. They were first described in 1845 by German physicist Gustav Kirc ...

, because conservation of current means current can split or combine at these points. When clarification is needed, a region connecting only two circuit elements is referred to as a simple node, where there is no branching of current, while a point connecting three or more elements is a ''principal node''. The full definition uses in this article encompasses both principal and simple nodes.

Details

According to

Ohm's law Ohm's law states that the electric current through a Electrical conductor, conductor between two Node (circuits), points is directly Proportionality (mathematics), proportional to the voltage across the two points. Introducing the constant of ...

, , the

voltage Voltage, also known as (electrical) potential difference, electric pressure, or electric tension, is the difference in electric potential between two points. In a Electrostatics, static electric field, it corresponds to the Work (electrical), ...

across any two points of a node with negligible resistance is :

V = IR = I\cdot 0 = 0,

showing that the

electric potential Electric potential (also called the ''electric field potential'', potential drop, the electrostatic potential) is defined as electric potential energy per unit of electric charge. More precisely, electric potential is the amount of work (physic ...

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 In electrical engineering, 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 accu ...

* The difference in voltage between

ground and neutral In electrical engineering, ground (or earth) and neutral are circuit conductors used in alternating current (AC) electrical systems. The neutral conductor carries alternating current (in tandem with one or more ''phase '' conductors) during ...

, between the

neutral wire In electrical engineering, ground (or earth) and neutral are circuit conductors used in alternating current (AC) electrical systems. The neutral conductor carries alternating current (in tandem with one or more ''phase '' conductors) during ...

and the

ground Ground may refer to: Geology * Land, the solid terrestrial surface of the Earth * Soil, a mixture of clay, sand and organic matter present on the surface of the Earth Electricity * Ground (electricity), the reference point in an electrical circ ...

domestic AC power plugs and sockets AC power plugs and sockets connect devices to mains electricity to supply them with electrical power. A plug is the connector attached to an electrically operated device, often via a cable. A socket (also known as a receptacle or outlet) is fi ...

, 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 Aluminum building wiring is a type of electrical wiring for residential construction or houses that uses Aluminum conductor, aluminum electrical conductors. Aluminum provides a better conductivity-to-weight ratio than copper, and therefore is al ...

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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