Kirchhoff's Current Law

Steps:

• Recognize the statement describes currents balancing at a node.
• Recall Kirchhoff's first law (KCL) states sum of currents in equals sum out at a junction.
• Note KCL derives from charge conservation, as charge can't accumulate at a point.
• Confirm Kirchhoff's second law (KVL) applies to voltages around a loop, not currents.

Why A is correct:

• KCL, Kirchhoff's first law, mandates ∑I_in = ∑I_out at a node, directly from charge conservation principle.

Why the others are wrong:

• B: Links first law to energy conservation, but KCL stems from charge conservation.
• C: Assigns current balance to second law, but that's KVL for voltages.
• D: Misattributes to second law and energy conservation, confusing KVL's basis.

Final answer: A