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Select the correct answer out of the options given against each question and write in the box provided on rigth hand side bottom:
A wire is stretched by `1%` but volume remains constant, then

A

resistivity increases by 1%

B

resistance increases by 2%

C

resistivity decreases by 1%

D

resistance decreases by 2%

Text Solution

Verified by Experts

Volume, V = `al` = constant, where `alpha` = cross sectional area.
Resistivity does not change due to elongation.
Resistance, R = `rho(l)/(alpha) = rho (l^(2))/(alphal) = rho (l^(2))/(V)`
As `rho` and V are constants,
`(Delta R)/(R ) = 2 (Delta l)/(l) = 2 xx 1% = 2 % `
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