Currents entering a node sum to zero because charge is conserved.
Charge cannot accumulate at a node, so the sum of currents entering equals the sum leaving: ΣI=0. It is used to write node equations and is valid for any lumped circuit, linear or not.
If 3 A and 2 A enter a node, 5 A must leave.
This law is the bookkeeping rule behind node analysis, and it shows that charge cannot accumulate at a junction.
Currents entering a node sum to zero because charge is conserved.
This law is the bookkeeping rule behind node analysis, and it shows that charge cannot accumulate at a junction.
Yes. It holds at every instant for any lumped circuit, because charge is conserved.
You may assign directions arbitrarily. A negative answer simply means the actual current flows opposite to your assumed direction.
Typical applications include solving the branch currents at a wiring junction in a power board, checking a measured current balance around a sensor node and writing node equations for an amplifier circuit.
Study "Parallel circuits" first (topic 9 of 106 in Electrical Engineering). It covers the groundwork this topic builds on.
Assign directions arbitrarily. Negative result means opposite direction. Supernodes include voltage sources.
If 3 A and 2 A enter a node, 5 A must leave.
The next topic is "Kirchhoff's voltage law", which builds directly on this one.
It is classed as Beginner in Electrical Engineering (topic 10 of 106). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.
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