Kirchhoff's First Law Conserves Charge at Junctions

Steps:

• Kirchhoff's first law (KCL) states the algebraic sum of currents at a junction is zero.
• This equality ensures no net charge buildup or depletion at the junction.
• Charge cannot be created or destroyed, so incoming current must equal outgoing current.
• Thus, KCL directly follows from charge conservation.

Why A is correct:

• KCL requires total current entering a junction to equal total current leaving, upholding the principle that charge is conserved in electrical circuits.

Why the others are wrong:

• B: Energy conservation applies to Kirchhoff's second law (KVL), which balances voltages around a loop.
• C: Momentum conservation is irrelevant to steady-state circuit analysis.
• D: Potential difference (voltage) is not a conserved quantity; it's the driving force in circuits.

Final answer: A