A wire is stretched so as to change its diameter by `0.25%` . The percentage change in resistance isA. `4.0%`B. `2.0%`C. `1.0%`D. `0.5%`

A wire is stretched so as to change its diameter by `0.25%` . The perc

1.	A wire is stretched so as to change its diameter by `0.25%` . The percentage change in resistance isA. `4.0%`B. `2.0%`C. `1.0%`D. `0.5%`
Answer» Correct Answer - C On stretching, volume (V) remains constant. So, V = Al or l = V/A Now, `R=(rho l)/(A)=(rho V)/(A^(2))=(rho V)/(pi^(2)D^(4)//16)=(16rho V)/(pi^(2)D^(4))` Taking logarithm of both the side and differentiating it, we get `(Delta R)/(R )=-4 (Delta D)/(D)` or `(Delta R)/(R )=-4xx(-0.25)=1.0%`

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