Three identical filament bulbs A, B, and C (each labelled “4 Ω when operating”) are wired to an ideal 12 V battery as follows:
• Bulb A is placed in series with a parallel branch that contains bulbs B and C.
A switch S is wired so that, when closed, it completely bypasses bulb C (providing a conducting path of negligible resistance around that bulb). Assume the bulbs reach their operating resistances quickly.
(a) With switch S open, determine the magnitude of the current leaving the battery.
(b) With switch S still open, rank bulbs A, B, and C from brightest to dimmest and justify your ranking.
(c) The switch S is now closed. Predict how the brightness of each bulb changes, if at all, and rank the bulbs again. Provide reasoning that traces how current and potential difference for each bulb are affected by closing the switch.