Increasing parallel resistance boosts lower branch voltage share

Steps:

• Variable resistor R parallels the lower resistor in the potential divider, shunting current through it.
• Increasing R raises the equivalent lower resistance, reducing shunting and increasing its share of total resistance.
• Voltage V2 across lower branch rises per V2 = V_total × (R_lower_eq / R_total).
• Voltage V1 across upper branch falls, as its share decreases with rising R_total.

Why B is correct:

• B matches the potential divider rule: V1 drops as upper fraction shrinks, V2 rises as lower fraction grows.

Why the others are wrong:

• A: Both decrease – V2 actually increases with less shunting.
• C: V1 increases, V2 decreases – reverses the resistance effect on voltage shares.
• D: Both increase – violates fixed total voltage, where gains in one cause losses in the other.

Final answer: B