A battery of emf V supplies two parallel branches. Branch 1 contains only a 50Ω fixed resistor R1. Branch 2 contains a 25Ω lightbulb B in series with a variable resistor Rv. The resistance of Rv is slowly increased from 0Ω to 75Ω. Assume the battery voltage remains constant and its internal resistance is negligible.
Which statement best describes how the currents in the two branches change as Rv is increased?
(a) Both branch currents decrease by the same factor as Rv increases because the total circuit resistance increases.
(b) Both branch currents remain constant because the battery voltage does not change.
(c) The current in Branch 1 remains the same, while the current in Branch 2 decreases.
(d) The current in Branch 1 increases while the current in Branch 2 decreases, since current that cannot pass through Branch 2 is redirected into Branch 1.