Parallel Path Increases Total Current, Diverts Branch Current

Steps:

• Assume standard circuit: battery connected to ammeter X in series with parallel branches; one branch has ammeter Y and resistor, other branch has switch and resistor.
• Before closing switch: current through X equals current through Y (single path).
• Closing switch adds parallel path, reducing total resistance, so current through X increases.
• Current through Y decreases as it shares with new parallel path (inverse to resistance ratio).

Why C is correct:

• By Kirchhoff's current law, total current rises with lower equivalent resistance, but branch current divides inversely proportional to resistances (I = V/R).

Why the others are wrong:

• A: Y increases wrongly; parallel path diverts current from Y.
• B: Both decrease wrongly; total current must increase with added path.
• D: Y increases wrongly; it loses current to parallel branch.

Final answer: C