Kirchhoff's Laws from Conservation Principles

Steps:

• Identify Kirchhoff's first law (KCL) as the junction rule, stating sum of currents entering a node equals sum leaving.
• Recognize KCL derives from conservation of electric charge, expressed as steady-state current balance.
• Identify Kirchhoff's second law (KVL) as the loop rule, stating algebraic sum of voltages around a closed loop is zero.
• Recognize KVL derives from conservation of energy, as work done by electric fields equals potential differences.

Why B is correct:

• KCL conserves current (charge flow rate); KVL conserves energy via voltage sums equaling zero, per electrostatic potential definitions.

Why the others are wrong:

• A: Reverses laws; charge conservation underlies current, not vice versa, and second law is energy, not current.
• C: Mass conservation irrelevant to electric circuits, which involve charge and energy.
• D: Reverses laws; first is current/charge, not energy.

Final answer: B