Question 18.AP.2: LIGHTBULB COMBINATIONS Compare the brightness of the four id...

College Physics

LIGHTBULB COMBINATIONS

Compare the brightness of the four identical lightbulbs shown in Figure 18.10. What happens if bulb A fails and so cannot conduct current? What if C fails? What if D fails?

18.10

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Bulbs A and B are connected in series across the emf of the battery, whereas bulb C is connected by itself across the battery. This means the voltage drop across C has the same magnitude as the battery emf, whereas this same emf is split between bulbs A and B. As a result, bulb C will glow more brightly than either of bulbs A and B, which will glow equally brightly. Bulb D has a wire connected across it—a short circuit—so the potential difference across bulb D is zero and it doesn’t glow. If bulb A fails, B goes out, but C stays lit. If C fails, there is no effect on the other bulbs. If D fails, the event is undetectable because D was not glowing initially.

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