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PHYSICS QUESTION
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Answer 1

Answer:

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Answer 2

Given:-

Length of wire is 1 m.

Resistance of wire = 26 Ω

Diameter of wire = 0.3mm or 3 × 10-⁴ m

To find :-

Resistivity of metal wire

Solution:-

Since, the temperature is constant 20°c so there is no change in resistance of the wire.

We used here the relation between resistivity and resistance.

★ $\large</strong><strong>\</strong><strong>g</strong><strong>r</strong><strong>e</strong><strong>e</strong><strong>n</strong><strong>{\underline{\boxed{ </strong><strong>R = p \frac{l}{a}</strong><strong>}}}$

where R is resistance,

p is resistivity,

l is length and a is area of wire.

area of wire = πr²

= $\pi \: ( { \frac{d}{2}) }^{2}$

$\implies$ $= \pi \: ( { \frac{(3 \times {10}^{ - 4}) }{2} }^{2} )$

$\implies$ $\pi \: \frac{9 \times {10}^{ - 8} }{4}$

Now,

Put the given value ,

★$\large\red{\underline{\boxed{p = \frac{ra}{l}}}}$

$\implies$ $p = \frac{26 \times \pi \times 9 \times {10}^{ - 8} }{4l}$

$\implies$ $p = \frac{26 \times 9 \times {10}^{ - 8} \times 314 }{100 \times 4 \times 1}$

$\implies$ $p = 1.84 \times {10}^{ - 8} \times {10}^{ - 2} \times {10}^{ - 4}$

$\implies$ $p = 1.84 \times {10}^{ - 6</strong><strong>}$Ωm

hence, the resistivity of wire is$p = 1.84 \times {10}^{ - 6}$Ωm

From table we can see that the material is manganese.