VsubA

VsubA is a notation used in electrical engineering and circuit theory to denote the voltage at a specific node, labeled A, in an electrical circuit. It represents the electric potential of node A relative to a chosen reference node, typically ground. In many texts, this quantity is written as V_A or V_sub_A, with VsubA specifically emphasizing the subscripted node.

The value of VsubA depends on where the reference node is defined. If the reference is ground, VsubA is simply the voltage of node A with respect to ground. More generally, VsubA equals the potential at node A minus the potential of the reference node: VsubA = V(node A) − V(reference). This convention allows multiple node voltages to be described consistently within the same circuit.

In circuit analysis, VsubA is treated as a variable to be determined. It is commonly solved using Kirchhoff's laws, nodal analysis, or other circuit techniques. For example, in a network where node A connects to ground through resistor R1 and to node B through resistor R2, the node-voltage equation at A may be written as (VsubA − 0)/R1 + (VsubA − VsubB)/R2 = 0, assuming passive sign convention. The specific values depend on the network, the components, and the defined reference.

VsubA is a convenient label on schematics and in equations to track the potential at a particular node without mixing it with currents or other voltages. It is part of the broader concept of node voltages used in nodal analysis.

See also: node voltage, reference node, nodal analysis, Kirchhoff's laws.