Kirchhoff's Current Law, or

KCL, is a fundamental

law of

circuit theory. It states that the total of all

currents flowing into a node (or

supernode) of a

circuit must equal the total of all

current flowing out of the node (or

supernode). In other words, the

algebraic sum of all the

currents entering a

node must be 0.

This law is caused by twin facts: (1)charge must be conserved and (2)charge cannot accumulate at a node. Thus, since whatever charge enters a node cannot be destroyed, and it cannot accumulate, it must leave. Since current is merely charge/time, KCL follows.

Typically, one uses KCL to determine some unknown current flowing into or out of a node, having other currents known. By simultaneously solving many KCL equations, one can perform node voltage analysis.

See also circuit, Kirchhoff's Voltage Law, current density, Kirchhoff, Gustav Robert.

Also **very** commonly misspelt Kirchoff's Current Law--about 40% of the time according to some quick searches I did on Google. (It caught me.)