CBSE Class 10 Answered
When the wire is streched 3 times the length then the length increase and the area of cross section also decrease therefore the resistance increase.
Asked by vedantkulkarni499 | 06 Aug, 2019, 07:51: PM
Expert Answer
Resistance = ρ×L/A ................(1)
where ρ is resistivity of material , L is length of wire and A is area of cross section.
when we stretch the wire so that length increases 3 times, for a given volume V,
its cross sectopn area decreases by 1/3 of its initial value.
stretched length L' = 3L and reduced area A' = (1/3)A
hence modified resistance R' = ρ×L' / A' = ρ×(3L)/ [ (1/3)A ] = 9×ρ×L/A ..................(2)
By comparing eqn. (1) and eqn.(2), we get modified resistance R' = 9R
Answered by Thiyagarajan K | 06 Aug, 2019, 10:27: PM
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