We stretch a wire of resistance R such that its length increases by 20%. Then the percentage change in its resistance will be?
A
20%
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B
44%
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C
10%
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D
40%
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Solution
The correct option is B 44% New length = 1.2L
When we stretch a wire to increase it's length without changing it's volume then: R1R2=(l1l2)2⇒R1R2=(L1.2L)2=11.44 R2=1.44R1Ω ∴Percentage change in R=R2−R1R1×100⇒44%