Question

A cylinderical wire is stretched to increase its length by 10%.calculate the percentage increase in resistance

Answer 1

Answer:

21%

explanation:

R=rho× L/A

when we are stretching both l and A will change.

But in this question increase in length is only given. So, we convert the above the equation from 2 variable to 1 variable by multiplying l on numerator and denominator of R. H. S

=>

R=rho× L^2/V [ V= A×L]

when stretching volume won't change.

Ri=rho( L^2/V)

Rf= rho (L+10/100L)^2/V

Rf= rho (11/10L)^2/V

Rf= rho (121/100L^2) /V

Rf/Ri=121/100

(Rf/Ri)-1 = (121/100)-1

(Rf-Ri)Ri= 21/100

(Rf-Ri) /Ri × 100= 21%

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