Classical Theory of Conduction Find (a) the current density and (b) the drift ve
ID: 1559673 • Letter: C
Question
Classical Theory of Conduction Find (a) the current density and (b) the drift velocity if there is a current of 1 mAin Number 14 copper wire (diameter = 0. 163 cm). Classical Theory of Conduction How long would it take for an electron to travel a city block (-160 m) it it were moving through a #10 Cu wire (0.102 inches dia) with 10 volts across its end. Use a Cu resistivity of 1.7 mu W cm and carrier density of 9 times 10^22 cm^-3. Quantum Theory of Conduction What is the Fermi speed, that is the speed of a conduction electron whose energy is equal to the Fermi energy for Na, Au, and Sn. See Table 10.2(3) in tippler. Band Diagram Draw simple band diagrams with appropriate labels (E_f, E_c, E_v) for a metal and a p-type semiconductor. Include the dopant energy level for the semiconductor. Explain how and why the resistivity of each material changes as the temperature increases. Semiconductor Dopants (a) What are donor and acceptor impurities in a semiconductor and why are they used? (b) If a donor dopant is to be thermally ionized at room temperature, then how far can its energy level be located below the conduction band (in eV). Hall Effect When a p-type silicon device (2 mm wide, 10 cm long, 350 mu m thick) is placed in a 3 Tesla perpendicular magnetic field and 1 A flows along its length, a Hall voltage of 50 mu V is measured across its width. Find the carrier density of this device. Also, draw a picture of the device with the F qv times B and the Hall voltage polarity indicated (+ and -), assuming that the B field points into of the page and the current flows right to left. Devices Briefly describe an LED and solar cell. Include simple band diagrams of each that show the electron transitions due to the interacting photon. pn Diode Find the room temperature resistance of a Si diode at 0.8V in forward and reverse bias. Assume I_0 = 0.1 mu A and kT = 26 me V at room temperature. By referring to your results for these resistances, explain why a diode is "rectifying" or a one-way device.Explanation / Answer
1) a) i = 1 * 10-3 A, d = 0.163 * 10-2 m
r = d /2 = 8.15 * 10-4 m
Number of atoms n = p N / M = (8920 * 6.023 * 1026) / (63.5) = 8.46 * 1028 /m3
Current density = I / A = I / pi r2 = (1 * 10-3) / (pi * (8.15 * 10-4 )2)
= 479 A/m2
b) Drift velocity = J / ne = (479) / (8.46 * 1028 * 1.6 * 10-19 )
= 3.54 * 10-8 m/s