Q146 / 160 · TS EAMCET 2022 (18 Jul Shift 2) · Physics

A cylindrical metallic wire is stretched to increase its length in such a way that the metallic wire changes its resistance by 6%. The percentage increase in its length is

  • A
    2%
  • B
    4%
  • Correct answer
    C
    3%
  • D
    12%

Solution

Resistance of a uniform wire is given by,

R=ρLA.

As volume will remain constant, therefore,

AL=V⇒A=VL

So we can write resistance as,

R=ρLVL=ρVL2

Now for small changes we can write,

∆RR=2∆LL⇒∆LL×100=12∆RR×100=12×6=3%

Hence, the correct answer is option: 'C'.

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