# A network of three 5-Ω resistors cannot have an equivalent resistance of

1. 7.5 Ω
2. 2.5 Ω
3. 1.67 Ω
4. 15 Ω

## A network of three 5-Ω resistors cannot have an equivalent resistance of

A network of three 5-Ω resistors cannot have an equivalent resistance of 2.5 Ω.

1. Three options are possible for three resistors
1. first option for three resistors: three resistors are in series then
2. Req = 5 + 5 + 5 = 15Ω
3. second option for three resistors: three resistors are in parallel then
4. 1/Req = 1/5 + 1/5 + 1/5 = 3/5 Ω and Req = 5/3Ω = 1.67Ω
5. third option for three resistors: two resistors are parallel and and one is series
6. 1/Req = 1/5 + 1/5 = 2/5Ω and Req = 5/2Ω = 2.5Ω
7. the above resistance are series with third resistors
8. Req = 2.5Ω + 5Ω = 7.5Ω
9. Conclusion: these three resistances 15Ω, 1.67Ω, and 7.5Ω are possible.
10. so, the correct answer is 2.5Ω which is not possible.

This question is about MSc Electricity and Magnetism MCQs. This is the previous year’s question about the competitive exams.

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