Kirchhoff's First Law Conserves Charge at Junctions

Steps:

• Recall Kirchhoff's first law as the junction rule: algebraic sum of currents entering a junction equals zero.
• Link this to conservation of charge, as charge cannot accumulate at a point in steady state.
• Examine options: A matches the junction rule statement and charge conservation.
• Eliminate others: B misnames conserved quantity; C and D describe the loop rule (second law).

Why A is correct:

• Kirchhoff's Current Law (KCL) states the algebraic sum of currents at a junction is zero, directly from the principle that electric charge is conserved in a circuit.

Why the others are wrong:

• B: Junction rule is correct, but it conserves charge, not energy.
• C: Describes voltage law (second law), which does not conserve charge.
• D: Correctly identifies voltage law and energy conservation, but that's not the first law.

Final answer: A