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If a copper wire of 200 m length having 0.44mm diameter has resistance of 20 Ohm, then find its specific resistance (in Ohm-m).

If a copper wire of 200 m length having 0.44mm diameter has resistance of 20 Ohm, then find its specific resistance (in Ohm-m). Correct Answer 1.520 × 10-8

A = 3.14×d2/4 and resistivity = R×A/l, where ‘A’ is the area of cross section of wire, ρ is specific resistance, R = resistance, d = diameter, l = length. Thus, A = 3.14×d2/4 = 3.14×(0.44)2/4 = 0.152 mm2, resistivity = R×A/l = (20×0.152/200) × 10-6 = 1.520 × 10-8.

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