Question

A copper wire has a resistancr of 0.5W. Another copper wire is of the same mass as the first but double in length. Find the resistance of the second wire?

Answer 1

since mass is equal.
both are same matterials so density is same
m1 =m2
d*v1 =d*v2. here v means volume and d= density.
v1=v2
a1*l1=a2*l2. since volume of wire =area*length

a1*l =a2*2l
a1 =2a2

so r1:r2=(l1*a2)/(l2*a1)
=l*a2/2l*2a2 =1/4
then r2=4*.5=2ohms