Kirchhoff's Circuit Laws
Kirchhoff's current and voltage laws explained with worked examples, the sign conventions that trip people up, and how to use them to solve a circuit.
Questions people ask
When do Kirchhoff's laws stop working?
At high frequencies, where the circuit is a meaningful fraction of a wavelength and radiation matters. For everything at audio and mains frequencies they hold exactly.
Which law should I use?
KCL for nodes where branches meet, KVL for loops. Node analysis with KCL usually needs fewer equations for circuits with many parallel branches.
What if I guess a current direction wrong?
Nothing breaks. The algebra returns a negative value, which tells you the real current flows the other way.
Does this page work offline?
Yes, after the first visit. The service worker caches it, so the reference stays available with no connection.
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Last updated 22 August 2026