Voltage Division Across Variable Potentiometer

Steps:

• Circuit has 4V battery, 1Ω fixed resistor, and 0–3Ω potentiometer in series.
• Total resistance varies from 1Ω (potentiometer at 0Ω) to 4Ω (potentiometer at 3Ω).
• Current varies from 4A (at 1Ω total) to 1A (at 4Ω total).
• Potential difference across X–Y (potentiometer) = current × potentiometer resistance, ranging from 4A × 0Ω = 0V to 1A × 3Ω = 3V.

Why A is correct:

• By Ohm's law, maximum voltage across 3Ω potentiometer is 3V at 1A current when total resistance is 4Ω, with minimum 0V at zero potentiometer resistance.

Why the others are wrong:

• B: Exceeds 3V maximum due to fixed 1Ω resistor dropping 1V at full potentiometer resistance.
• C: Minimum is 0V when potentiometer resistance is zero, not 1V.
• D: 10V impossible as it exceeds battery emf of 4V.

Final answer: A