Question

please guies answer my question
and explain..

Answer 1

$\huge{HEY MATE!!!}$

⚫ HERE IS UR ANSWER⬇⬇⬇

▶ R = 25 ohm,

▶ L = 1 m,

▶ D = 0.3 mm = 3 x 10-4m

▶ radius r = D/2 = 1.5 x 10-4m

▶ A = pi*r2= pi*(1.5 x 10-4)(1.5 x 10-4) = pi * 2.25 x 10-8m2

▶ resistivity = R X A / L = 25 x pi * 2.25 x 10-8/ 1

resistivity = 1.76 x 10-6ohm-m

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❇▶ For the second part, the resistivity is same. But to avoid long calcuations let us take ratio of resistances in second and first case, so that resistivity is cancelled.

▶ R2/ R1= (L2/ A2) / (L1/ A1) = L2A1/ L1A2

R2= R1x [L2A1/ L1A2]

⚫ The ratio of cross-section areas are proportional to the square of their diameters.

R2= 25 x 3 x (0.3)2/ 1 x (0.5)2

R2= 25 x 3 x 9 / 25

⭐ R2= 27 ohm ⭐

Hope it helps.

CHEERS!!!