Física 2 - Lista 3 - 2

18) i_A = 200 μA + 200 x 10^{-6} A\n i_B = i_A - 200 x 10^{-7} A\n i_C = -g_A - 200 x 10^{-6} C\ny = n - c = 200 x 10^{-6} - 1.6 x 10^{-10} = m = 200 x 10^{-6} - m = 1.25 x 10^{15} electrons.\n\n20) i = 50 mA\n V = 50 x 10^{3} \n R = 100Ω\n\n21) l = 4 mm\nd_0 = 0.2 mm\n R = 15 mm\n V = 23V\n R = 0.5 Ω\n\n22) σ = 1 / ρ\n l = 1.0 m\n R = 20Ω\n R = 0.5 m\n M = 2.0V\n I = 4.0A\n σ = 1 / 5 x 10^{-1}\n σ = 2 x 10^{-4} (ohm)^{-1}\n\n23) MV = 220V\n P = IV\n I = 9.8 kW\n R = P / I^2 \n I = 20A\n I = 15A\n A) MV = 220V, P=6.2A, R = 5Ω\n b) P = V·I\n V = R·I\n V = 140 20A\n 110 + R = 10A\n I = 4.2 kW