A rod of semiconducting material of lenght L=3 m and cross-sectional area A=4.5 mm^2 lies along the x-axis between x=0 and x=L. The material obeys ohm's law, and resistivity varies along the rod according to p=p0 (1-(x^2/L^2)) where p0= 4.10^-4 ohm.m. The end of the rod x=0 is at a potential V0=30V greater than the x=L. A) what is the total resistance, in units of ohm, of the rod? B) what is the current, in units of miliamperes, in the rod?  C) what is the electric potential, in units of Volt, in the rod at x=L/2?

Question A2 Pure copper has a resistivity of 1.68 x 10-8 Nm. Some accurate cubes of copper are prepared, and electrical measurements are made, for which current is passed across a pair of opposite faces. a) Comparing a 2.5 cm cube and a 5 cm cube, which will have the higher conductance? Ex- plain your answer. b) Given eight 1 cm cubes, how can they be stacked to get the highest and the lowest resis- tance between opposite faces of the stack? Calculate the resistance of each stack.

1.3 x 1020 electrons flow through a cross section of a 2.1-mm-diameter iron wire in 5.0 s. ▾ Part A What is the electron drift speed? Express your answer in micrometers per second. ▸ View Available Hint(s) IVD ΑΣΦ 2d=1.77.10-⁹ -9 Submit Previous Answers ? * Incorrect; Try Again; 2 attempts remaining μm/s

(a) A 35.1-m length of copper wire at 20.0°C has a radius of 0.23 mm. If a potential difference of 7.0 V is applied across the length of the wire, determine the current in the wire. (Use the values in the following table.) Resistivities and Temperature Coefficients of Resistivity for Various Materials (at 20°C) Material Resistivity(Ω · m) Temperature Coefficientof Resistivity [(°C)−1] Silver 1.59 ✕ 10−8 3.8 ✕ 10−3 Copper 1.7 ✕ 10−8 3.9 ✕ 10−3 Gold 2.44 ✕ 10−8 3.4 ✕ 10−3 Aluminum 2.82 ✕ 10−8 3.9 ✕ 10−3 Tungsten 5.6 ✕ 10−8 4.5 ✕ 10−3 Iron 10.0 ✕ 10−8 5.0 ✕ 10−3 Platinum 11 ✕ 10−8 3.92 ✕ 10−3 Lead 22 ✕ 10−8 3.9 ✕ 10−3 Nichromea 150 ✕ 10−8 0.4 ✕ 10−3 Carbon 3.5 ✕ 10−5 −0.5 ✕ 10−3 Germanium 0.46 −48 ✕ 10−3 Silicon 640 −75 ✕ 10−3 Glass 1010–1014   Hard rubber ≈1013   Sulfur 1015   Quartz (fused) 75 ✕ 1016   aA nickel–chromium alloy commonly used in heating elements.  ??A(b) If the wire is heated to 36.0°C while the 7.0-V potential difference is…

(a) A 34.9-m length of copper wire at 20.0°C has a radius of 0.29 mm. If a potential difference of 7.0 V is applied across the length of the wire, determine the current in the wire. (Use the values in the following table.) Resistivities and Temperature Coefficients of Resistivity for Various Materials (at 20°C) Material Resistivity(Ω · m) Temperature Coefficientof Resistivity [(°C)−1] Silver 1.59 ✕ 10−8 3.8 ✕ 10−3 Copper 1.7 ✕ 10−8 3.9 ✕ 10−3 Gold 2.44 ✕ 10−8 3.4 ✕ 10−3 Aluminum 2.82 ✕ 10−8 3.9 ✕ 10−3 Tungsten 5.6 ✕ 10−8 4.5 ✕ 10−3 Iron 10.0 ✕ 10−8 5.0 ✕ 10−3 Platinum 11 ✕ 10−8 3.92 ✕ 10−3 Lead 22 ✕ 10−8 3.9 ✕ 10−3 Nichromea 150 ✕ 10−8 0.4 ✕ 10−3 Carbon 3.5 ✕ 10−5 −0.5 ✕ 10−3 Germanium 0.46 −48 ✕ 10−3 Silicon 640 −75 ✕ 10−3 Glass 1010–1014   Hard rubber ≈1013   Sulfur 1015   Quartz (fused) 75 ✕ 1016   (b) If the wire is heated to 32.0°C while the 7.0-V potential difference is maintained, what is the resulting current in the wire?