Question

A wire of resistance 1 ohm and resistivity 'p' (roh) is stretched to double it's length. What will be it's new resistance and resistivity.

Answer 1

resistance = 1ohm
r = pl/a .....(1)
new resistance of
l'= 2l
a' = a/2 { l×a= l' × a' (cause volume remains same) =》 l×a = 2l×a' ----》 a= 2 a' ---》 a'= a/2}
new resistance==》

r' = pl'/ a'
r' = p (2l) / a/2
r' = p4l/a
r' = 4r { coz of eq 1)
r' = 4 × 1
r' = 4 ohm
hope it helps u
Nd tell me of this is crrect ! or wrong!