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A Piece of wire of resistance 29 ohm is drawn out so that its length increased to twice its original length. calculate the resistance of

the wire in the new situation.


R= \frac{pl}{A}=29
when l'=2l
so R'= \frac{pl'}{A'}=4 \frac{pl}{A}=4(29)=116
so new resitance is 116 ohm
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R = pl/A

p=density , l=length , A = area

Multiplying l to both numerator and denominator,

R = pl^2 / V

V = Volume

R proportional to l^2

So when l is doubled , R becomes 4 times.

So R=116 ohm
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