An aluminium wire is stretched to make its length, 0.4% larger. The percentage change in resistance is:

<p>Volume = constant</p><p><span class="mathml" contenteditable="false"> <math> <mrow> <mi>A</mi> <mi mathvariant="script">l</mi> <mo>=</mo> <mi>C</mi> </mrow> </math> </span>&nbsp;</p><p><span class="mathml" contenteditable="false"> <math> <mrow> <mi>A</mi> <mi>d</mi> <mi mathvariant="script">l</mi> <mo>+</mo> <mi mathvariant="script">l</mi> <mi>d</mi> <mi>A</mi> <mo>=</mo> <mn>0</mn> </mrow> </math> </span>&nbsp;</p><p><span class="mathml" contenteditable="false"> <math> <mrow> <mfrac> <mrow> <mi>d</mi> <mi mathvariant="script">l</mi> </mrow> <mrow> <mi mathvariant="script">l</mi> </mrow> </mfrac> <mo>+</mo> <mfrac> <mrow> <mi>d</mi> <mi>A</mi> </mrow> <mrow> <mi>A</mi> </mrow> </mfrac> <mo>=</mo> <mn>0</mn> </mrow> </math> </span>&nbsp;</p><p><span class="mathml" contenteditable="false"> <math> <mrow> <mfrac> <mrow> <mi>d</mi> <mi>R</mi> </mrow> <mrow> <mi>R</mi> </mrow> </mfrac> <mo>×</mo> <mn>1</mn> <mn>0</mn> <mn>0</mn> <mo>=</mo> <mrow> <mo> (</mo> <mrow> <mfrac> <mrow> <mi>d</mi> <mi mathvariant="script">l</mi> </mrow> <mrow> <mi mathvariant="script">l</mi> </mrow> </mfrac> <mo>−</mo> <mfrac> <mrow> <mi>d</mi> <mi>A</mi> </mrow> <mrow> <mi>A</mi> </mrow> </mfrac> </mrow> <mo>)</mo> </mrow> <mo>×</mo> <mn>1</mn> <mn>0</mn> <mn>0</mn> </mrow> </math> </span>&nbsp;</p><p>= 0.4 - (-0.4)</p><p>= 0.8 %</p>

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