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
Medium
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$R \propto l$
Hence every new piece will have a resistance $\frac{R}{{10}}.$
If two pieces are connected in series, then their resistance $ = \frac{{2R}}{{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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