3.) A 20cm long tube has an inner diameter of 0.85cm and an outer diameter of 1.10cm. Find its electric resistance when used lengthwise,
(pcu = 1.7 x 10-m.)

The answer is below

Explanation:

The resistance of a conductor (R) is given by:

and ρ is resistivity

The length = 20cm = 0.2 m

The tube has an outer diameter of 1.1 cm (0.011 m), hence the outer area is:

A₁ = π * diameter²/4 = π * 1.1²/4 = 0.000095 m²

The tube has an inner diameter of 0.85 cm (0.0085 m), hence the inner area is:

A₂ = π * diameter²/4 = π * 0.0085²/4 = 0.0000567 m²

The conductor area = outer area - inner area = 0.000095 m² - 0.0000567 m² = 0.0000383 m²

Hence, the resistance is:

b would be the answer

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