Q26 of 36 Page 1

A student has two resistors- 2 Ω and 3 Ω. She has to put one of them in place of R2 as shown in the circuit. The current that she needs in the entire circuit is exactly 9A. Show by calculation which of the two resistors she should choose


The overall current needed = 9A.


The voltage is 12V Hence by Ohm’s Law V=IR,


The resistance for the entire circuit = 12/9 = 4/3 Ω. = R


Hence the net resistance for the entire circuit is 4/3 Ω


R1 and R2 are in parallel


Hence, R=(R1 R2)/(R1 + R2) = 4R2/(4+R2) = 4/3


and therefore


R2 = 2Ω


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