Question

A wire has resistance of 16 Ω . It is melted and drawn into a wire of half its length . Calculate the resistance of the new wire . What is the percentage change in its resistance ?

Answer 1

Explanation:

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Answer 2

Answer:

4Ω

Explanation:

Given:

Old resistance(r)=16Ω

New length(L)=$\frac{old length(l)}{2}$

New area of cross section(A)=2 Old area of cross section(a)

$\frac{A}{L}=4.a.l$

Resistivity does not change

To Find:

New resistance(R)

Now,

$\frac{r.a}{l} = \frac{R.A}{L}$

$\frac{16a}{l}=\frac{4Ra}{l}$

R=4Ω

Percentage change in resistance = $\frac{Change in resistance.100}{Initial resistance}$

                                                        =$\frac{12.100}{16}$

                                                        =75%

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