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Kirchhoff's junction rule (current law) is a direct result of which conservation law?

Conservation of charge: every bit of current into a node must come out.

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  1. Conservation of energy
  2. Conservation of charge ✔
  3. Conservation of momentum

Why: Current is moving charge, and charge cannot pile up or vanish at a junction. So the currents flowing in must add up to the currents flowing out.

Huh, didn't know that: A junction, also called a node, is a connection of three or more wires.

The dad joke
Why did the current go to the junction? It heard everyone was splitting up there.
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References

Answer: Conservation of charge. Current is moving charge, and charge cannot pile up or vanish at a junction. So the currents flowing in must add up to the currents flowing out.

  1. OpenStax University Physics Vol. 2, 10.3 Kirchhoff's Rules openstax.org/books/university-physics-volume-2/pages/10-3-kirchhoffs-rules
    The sum of all currents entering a junction must equal the sum of all currents leaving the junction.
    Checked 2026-10-10.

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