Kirchhoff's Second Law and Charge Conservation

Steps:

• Recall Kirchhoff's second law states that the algebraic sum of currents at a junction is zero.
• Recognize this implies no charge accumulation at the junction.
• Match to principles: conservation of charge means incoming current equals outgoing current.
• Eliminate options not describing charge balance.

Why B is correct:

• B directly states the junction rule, derived from charge conservation (∑I_in = ∑I_out at a node).

Why the others are wrong:

• A describes energy conservation, basis for Kirchhoff's first law (voltage rule).
• C provides no principle, making it invalid.
• D restates Ohm's law (V = IR) summed, not a foundational principle for any Kirchhoff law.

Final answer: B