Equivalent resistance determines total current

Steps:

• Identify ammeter measures total current from power supply.
• Calculate equivalent resistance (Req) for each arrangement using series (Req = sum) or parallel (1/Req = sum of 1/R) formulas.
• Apply Ohm's law: I = V / Req, where V is fixed; lowest Req yields highest I.
• Compare Req values across options to find minimum.

Why A is correct:

• All three resistors in parallel give lowest Req (1/Req = 1/R1 + 1/R2 + 1/R3), maximizing I per Ohm's law.

Why the others are wrong:

• B: All in series gives highest Req (sum of resistances), minimizing I.
• C: Two in series, then parallel with third gives moderate Req, lower I than A.
• D: Two in parallel, then series with third gives higher Req than A, reducing I.

Final answer: A