An aluminium rod and a copper rod are taken such that their lengths are same and their resistances are also same. The specific resistance of copper is
An aluminium rod and a copper rod are taken such that their lengths are same and their resistances are also same. The specific resistance of copper is half that of aluminium, but its density is three timesthat of aluminium. The ratio of the mass of aluminium rod and that of copper rod will be :-
A. `1//6`
B. `2//3`
C. `1//3`
D. 6
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Correct Answer - B
`(m_(Al))/(m_(Cu))=(A_(Al)Ld_(Al))/(A_(Cu)L d_(Cu))`
`rArr ([rho Al L^(2)(d_(Al))/(R ))/(rho CuL^(2)(d_(Cu))/(R )])`
`=(rhoAld_(Al))/(rhoCu d_(Cu))=(rho Al)/(((rhoAl)/(2)))=(d_(Al))/((3d_(Al)))=(2)/(3)`
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