Question : A wire of a certain material is streched slowly by ten percent. Its new resistance and specific resistance become respectively
a) both remain the same.
b) 1.1 times, 1.1 times.
c) 1.2 times, 1.1 times.
d) 1.21 times, same.
Doubt by Tannu
Solution :
l'=l+10% of l
l'=l+(10/100)l
l'=l+0.1l
l'=l+0.1l
l'=1.1l
We know, when a wire is streched by n times of its original length then its new resistance will become n² times the original resistance.
R'=n²R
R'=(1.1)²R
R'=1.21R
R'=n²R
R'=(1.1)²R
R'=1.21R
Hence, the new resistance will become 1.21 times the new resistance.
Also, we know that resistivity of a wire is independent of the dimensions of wire and depend only on the material of the wire. Hence, resistivity of the wire will remain same.
So, 'd) 1.21 times, same' would be the correct option.
