UnitExam3Asolutions

# UnitExam3Asolutions - ID A UCSD Physics 2B Answer Section...

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ID: A 3 UCSD Physics 2B Unit Exam 3A Current, Resistance, Circuits Answer Section MULTIPLE CHOICE 1. ANS: B This is a compound circuit, so we must find the current around the entire loop, and therefore the equivalent resistance of the entire circuit. First, reduce the parallel leg to its equivalent 1 R Parallel = 1 R 1 + 1 R 2 = 1 30.0 Ω + 1 30.0 Ω = 1 15.0 Ω so that R Parallel = 15.0 Ω This is in series with R 3, so R Series = R 1 + 2 + R 3 = 15.0 Ω + 30.0 Ω = 45.0 Ω The total circuit current is thus I = V R Series = 75.0 V 45.0 Ω = 1.67 A Since the entire circuit current must pass through R 3 , P 3 = I 2 R 3 = 1.67 A ( ) 2 30 Ω ( ) = 83.3 W TOP: NET + POWER 2. ANS: A R = V I 220 V 8.75 A = 25.1 Ω TOP: OHM'S LAW 3. ANS: B The resistors are in parallel, so they’re at the same voltage and independent of each other. P 2 = V 2 R 2 = 50.0 V ( ) 2 17.2 Ω = 145 W TOP: POWER

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