ID: A3UCSD Physics 2B Unit Exam 3A Current, Resistance, CircuitsAnswer SectionMULTIPLE CHOICE1. ANS: BThis 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 equivalent1RParallel=1R1+1R2=130.0Ω+130.0Ω=115.0Ωso that RParallel=15.0ΩThis is in series with R3, soRSeries=R1+2+R3=15.0Ω +30.0Ω =45.0ΩThe total circuit current is thus I=VRSeries=75.0V45.0Ω=1.67ASince the entire circuit current must pass through R3,P3=I2R3=1.67A()230Ω()=83.3WTOP: NET + POWER 2. ANS: AR=VI−220V8.75A=25.1ΩTOP: OHM'S LAW 3. ANS: BThe resistors are in parallel, so they’re at the same voltage and independentof each other.P2=V2R2=50.0V()217.2Ω=145WTOP: POWER
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