Question

a uniform wire of resistance 4.5 ohm is uniformly stretched to three times its original length. new resistance will be.

Answer 1

hope you got it right

Answer 2

Given that,

Resistance of a uniform wire, R = 4.5 ohms

The wire is  stretched to three times its original length.

To find,

New resistance of the wire.

Solution,

The resistance of a wire is directly proportional to its length. It is given by :

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

If length is stretched 3 times, l' = 3l

New resistance becomes,

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

R = 4.5 ohms

So,

$R'=3\times 4.5\\\\R'=13.5\ \Omega$

New resistance of the wire is 13.5 ohms.

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