SAT Subject Physics Practice Question 87: Answer and Explanation

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Question: 87


Determine the equivalent resistance between points a and b.

A. 0.167 Ω
B. 0.25 Ω
C. 0.333 Ω
D. 1.5 Ω
E. 2.0 Ω

Correct Answer: E


The 12 Ω and 4 Ω resistors are in parallel and are equivalent to a single 3 Ω resistor, because . This 3 Ω resistor is in series with the top 3 Ω resistor, giving an equivalent resistance in the top branch of 3 Ω + 3 Ω = 6 Ω. Finally, this 6 Ω resistor is in parallel with the bottom 3 Ω resistor, giving an overall equivalent resistance of 2 Ω, because .

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