Question

Calculate the resistance of 1 km long aluminium wire of diameter 5 mm. Find thesame for a wire made of nichrome alloy.(Given: Resistivity of aluminium = 2.8 x 10 m, VResistivity of nichrome = 100 x 10 m)​

Answer 1

length of aluminium wire, l = 1km = 1000m

resistivity of aluminium, p = 2.8 × 10^-8 ohm.m

diameter of wire, d = 5mm = 5 × 10^-3 m

so, cross sectional area of wire , A = π(d/2)² = π × (25 × 10^-6)/4 = 6.25π × 10^-6 m²

using formula, R = pl/A

= 2.8 × 10^-8 × 1000/(6.25π × 10^-6)

= 28/6.25π

=1.42 ohm

for nichrome :

length , l = 1000m, A = 6.25π × 10^-6 m²

and p = 100 × 10^-8 ohm.m

so, resistance of nichrome wire, R = pl/A

= 100 × 10^-8 × 1000/(6.25π × 10^-6)

= 1000/6.25π ≈ 51 ohm

Answer 2

Answer:

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