Question

a wire 1m long has a resistance of 1 ohms . it is uniformly stretched, so that its length increases by 25%, then its resistance will increase by?

Answer 1

R = pL/A

L= 1 m

1*25/100 = 0.25

New l= 1.25 m

Volume = L*A (constant here)

So if length becomes 1.25 m, area should decrease by 1.25.

R'= p 1.25(L)/A/1.25

= p (1.25)^2 L/A

= (1.25)^2 [p L/A]

= 1.5625 R (R = pL/A)

Therefore, increase in resistance = 56.25%

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