Decreasing variable resistance increases series circuit current

Steps:

• Circuit is series: battery (fixed emf V), lamp (fixed resistance R_lamp), variable resistor (R_var).
• Total resistance R_total = R_lamp + R_var.
• Decreasing R_var reduces R_total.
• Current I = V / R_total, so I increases.

Why A is correct:

• Ohm's law states current increases when total resistance decreases in a series circuit with fixed emf.

Why the others are wrong:

• B: Current is identical throughout series circuit, so it increases in resistor too.
• C: Battery emf remains constant regardless of resistance changes.
• D: Total resistance decreases as R_var is reduced.

Final answer: A