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2. What length of wire (sp. resistance 48 x 10^-8ohm m)is needed to make a resistance of 4.2 ohm?(Diameter 0.4 mm). |
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Answer» Given R = 4.2 ohmrho = 48 x 10^-8 ohm mr = d/2 = 0.4/2 = 0.2 mm = 2 x 10^-4 mpi = 22/7So needed L = pi r^2 R / rhoL = 22/7 * 4 * 10^-8 * 4.2 / 48 x 10^-8So L =1.1 m |
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