- 7.5 Ω
- 2.5 Ω
- 1.67 Ω
- 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.
- Three options are possible for three resistors
- first option for three resistors: three resistors are in series then
- Req = 5 + 5 + 5 = 15Ω
- second option for three resistors: three resistors are in parallel then
- 1/Req = 1/5 + 1/5 + 1/5 = 3/5 Ω and Req = 5/3Ω = 1.67Ω
- third option for three resistors: two resistors are parallel and and one is series
- 1/Req = 1/5 + 1/5 = 2/5Ω and Req = 5/2Ω = 2.5Ω
- the above resistance are series with third resistors
- Req = 2.5Ω + 5Ω = 7.5Ω
- Conclusion: these three resistances 15Ω, 1.67Ω, and 7.5Ω are possible.
- 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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