In the circuit shown in the figure, all the lightbulbs are identical. Which of the following is the correct ranking of the brightness of the bulbs?
A) B and C have equal brightness, and A is the dimmest.
B) A and B have equal brightness, and C is the dimmest.
C) A is brightest, C is dimmest, and B is in between.
D) A is the brightest, and B and C have equal brightness but less than A.
E) All three bulbs have the same brightness.

Question

In the circuit shown in the figure, all the lightbulbs are identical. Which of the following is the correct ranking of the brightness of the bulbs? 
A) B and C have equal brightness, and A is the dimmest. 
B) A and B have equal brightness, and C is the dimmest. 
C) A is brightest, C is dimmest, and B is in between. 
D) A is the brightest, and B and C have equal brightness but less than A. 
E) All three bulbs have the same brightness.

Quizplus · Accepted Answer

Since the circuit is in series, the same current flows through each lightbulb. Therefore, the brightness of the bulbs is determined only by their resistance. Bulb A has the least resistance because it has a shorter path to the battery's positive terminal. Therefore, it will be the brightest. The bulbs B and C have the same resistance because they are on identical paths. Thus, they will have an equal brightness, which will be less than bulb A's brightness. Therefore, the ranking of the brightness of the bulbs is: A > B = C.

In the Circuit Shown in the Figure, All the Lightbulbs