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B. When two resistors are connectedin series, their effective resistanceis 80 12. When they are connectedin parallel, their effective resistanceis 20 92. What are the values of thetwo resistances? |
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Answer» In series, R1 + R2 = 80in parallel, 1/R1 + 1/R2=1/20R1+R2/R1R2 = 1/2080/R1.R2 = 1/20R1.R2 = 1600put R2=80-R1R1(80-R1)=160080R1-R1^2 = 1600R1^2 - 80R1 + 1600=0R1^2 - 40R1- 40R1 + 1600=0R1(R1-40)-40(R1-40)=0(R1-40)(R1-40)=0R1=40 R2=80 R2=80-R1=80-40=40 ohm |
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