PHYS 272 Lecture Notes - Lecture 13: Short Circuit, Power Transform, Temperature Coefficient
12 Mar 2018
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Document Summary
Resistance r of any wire is directly proportional to its length, and inversely proportional to its cross section area, a. , where is a constant called resistivity and depends on the materials used. Conductivity, is the reciprocal of the resistivity where = For copper is 1. 68 x 10-8 m. A = r2 r = 1. 04 x 10-3 m. Diameter = 2r = 2 * 1. 4 x 10-3m. * what happen if a wire of resistance r is stretched to its length is doubles. As length is doubled, the cross section area is halved because the volume (v = a*l) stays the same. 1 the resistance increase by a factor of 4 ( Atoms interfere with the flow of electrons. * the resistance of metals increase with temperature. * when infinitesimal charge, dq, moves through a potential difference, energy is transformed. * o is the resistivity at some ref temperature, t. * is the temperature coefficient of resistivity.
