Question

8.
Resistance of a wire is 20 ohm. It is drawn
in such a way that it experiences a longitu-
dinal stress equals to Young's modulus nu-
merically. Its new resistance is
1) 60 ohm
2) 80 ohm
3) 120 ohm
4) 180 ohm​

Answer 1

Answer:

Given resistance = R1 = 20 ohm

Let length of the wire = L

Therefore, new length of the wire = 2L

Since, when the length is doubled, cross sectional area of the wire becomes half.

Therefore, new resistance = R = 2L/ (A/2) =4L/A

R = 4 x 20 (since, L/A = resistance)

R = 80 ohm.

Explanation:

May it helps you

Answer 2

Answer:

80ohm

Explanation:

r is directly proportional to its longitude so if longitudnal stress equal to young's modulus numerically then the new r will be 80ohm.