A) r
B) \[\frac{r}{\sqrt{2}}\]
C) \[\sqrt{5}\,r\]
D) 2r
Correct Answer: C
Solution :
As resistance, \[R=\frac{\rho l}{A}\] For wire x, \[20=\frac{\rho l}{\pi {{r}^{2}}}\] ... (i) Similarly, for wire y, \[8=\frac{\rho (2l)}{\pi {{(r'\,)}^{2}}}\] Dividing Eq. (i) by (ii), we have \[\frac{20}{8}=\frac{\rho l}{\pi {{r}^{2}}}\times \frac{\pi {{(r\,'\,)}^{2}}}{\rho \,(20)}\] \[5={{\left( \frac{r'}{r} \right)}^{2}}\,\,\,\Rightarrow \,\,\,r'=\sqrt{5}\,\,r\]You need to login to perform this action.
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