Question

wire of circular cross-section and 30 ohm resistance is uniformly stretched until its new length is three times
its original length. Find its resistance.​

Answer 1

Answer:

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Explanation:

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Answer 2

The new resistance of the wire is 90 ohms.

Explanation:

The resistance of a wire is given by :

$R=\rho\dfrac{l}{A}$

Resistance of the wire is 30 ohms. The wire is uniformly stretched until its new length is three times  its original length.

New length, l' = 3l

Area will remain the same. New resistance

$R'=\rho\dfrac{l'}{A}\\\\R'=\rho\dfrac{3l}{A}\\\\R'=3\times \rho\dfrac{l}{A}\\\\R'=3R\\\\R'=3\times 30\\\\R'=90\ \Omega$

So, the new resistance of the wire is 90 ohms. Hence, this is the required solution.

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