SAT Subject Physics Practice Question 88: Answer and Explanation

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Question: 88

6.

Three identical light bulbs are connected to a source of emf, as shown in the diagram above. What will happen if the middle bulb burns out?

A. All the bulbs will go out.
B. The light intensity of the other two bulbs will decrease (but they won’t go out).
C. The light intensity of the other two bulbs will increase.
D. The light intensity of the other two bulbs will remain the same.
E. More current will be drawn from the source of emf.

Correct Answer: D

Explanation:

If each of the identical bulbs has resistance R, then the current through each bulb is ε /R. This is unchanged if the middle branch is taken out of the parallel circuit. (What will change is the total amount of current provided by the battery.)

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