A) \[\frac{1}{6}\]
B) \[\frac{2}{3}\]
C) \[\frac{1}{3}\]
D) 6
Correct Answer: B
Solution :
Resistance of wire is given by \[R=\rho .\frac{1}{A}\] ???(i) where \[\rho \] is specific resistance of wire, A is area of cross-section of wire, and \[l\] is length of wire. If V is volume of wire, then \[R=\rho .\frac{{{l}^{2}}}{V}\] ...(ii) If d is density and m is mass of wire, then \[R=\rho .\frac{{{l}^{2}}d}{m}\] \[\therefore \] \[m\propto \rho d\] \[\therefore \] \[\frac{{{m}_{Al}}}{{{m}_{Cu}}}=\frac{{{\rho }_{Al}}}{{{\rho }_{Cu}}}\times \frac{{{d}_{Al}}}{{{d}_{Cu}}}\] \[=\frac{2}{1}\times \frac{1}{3}=\frac{2}{3}\]
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