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Question: Answered & Verified by Expert
A copper wire of resistance $R$ is cut into ten parts of equal length. Two pieces each are joined in series and then five such combinations are joined in parallel. The new combination will have a resistance
PhysicsCurrent ElectricityJEE Main
Options:
  • A $R$
  • B $\frac{R}{4}$
  • C $\frac{R}{5}$
  • D $\frac{R}{25}$
Solution:
1326 Upvotes Verified Answer
The correct answer is: $\frac{R}{25}$
Hence every new piece will have a resistance $\frac{R}{10}$. If two pieces are connected in series, then their resistance $=\frac{2 R}{10}=\frac{R}{5}$
If 5 such combinations are joined in parallel, then net resistance $=\frac{R}{5 \times 5}=\frac{R}{25}$

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