a material B has twice the specific resistance of a circular wire made up of B has twice the diameter of a wire made of a then for the two wires to have the same resistance the ratio lB upon IA of the respective length must be
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R=pL/A
we get p =RA/l=Rπd^2/4l
l=Rπd^2/p
l is proportional to d^2/p
lA/lB=d^2/p/4d^2/2p=1/2
then,lA/lB=2
hence the ans is 2
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