AP · AP 2 · multiple choice
AP Physics 2: Algebra-Based · Question 3
AP Physics 2: Algebra-Based · Original GioPhysics question with a detailed, mark-by-mark answer guide.
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multiple choice1 mark
Three identical light bulbs are connected to a battery of negligible internal resistance: bulb X is in series with a parallel combination of bulbs Y and Z. Bulb Z then burns out, breaking its branch. What happens to the brightness of bulb X?
- A
It becomes brighter.
- B
It becomes dimmer.
- C
It is unchanged.
- D
It goes out.
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Answer overviewCorrect answer: B — It becomes dimmer.
01
1 markAnswer and reasoning
How to approach it
Predict from the governing principle before looking for a matching option. Then reject alternatives by checking direction, units, limiting behaviour or the physical meaning of each statement.
- 1
The correct choice is B: It becomes dimmer.
- 2
Removing Z raises the total resistance of the circuit from 1.5R to 2R, so the current through X falls and X dims. A is chosen by candidates who reason that "fewer bulbs means more current for each", which is true for bulb Y's share but not for the total.
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