Question

A piece of wire of resistance 4 ohms is streched such that it's area of cross section becomes one forth of its original,then the resistance is
A 8 ohms
B 64 ohms
C 2 ohms
D 16 ohms

Answer 1

Answer :- Finally resistance became 16timed equal to 64 ohm .

Answer 2

d.16 is the ans

resitivity constant

length

A2=A1/4

R1/R2=pl/a/pl/a/4

4 goes up and pl and a gets cancelled as they are same

4/R2 =1/4

16ohms=R2