homework 11

# Modern Physics

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PHY251 Homework Set 11 Reading: Chapter 12, 14 (all sections except 6) Homework: Chapter 12, Problems 32, Chapter 14, Problems 2, 6(Li, Al, Cu only!),9(Li, Al, Cu only!),10,17,18,31 Hints and Solutions Problem XII.32 (15 points) Consider a free-electron gas at a temperature T such that kT << E F . Write down an expression for the electron number density N/V for electrons that have an energy in excess of E F . Show, by making the change of variables ( E - E F )/ kT = x , that the number density is proportional to T . Calculate an expression for N/V under these circumstances, making use of the fact that 0 (e x + 1) - 1 dx = ln 2. Hints: In working out the integral over E the integrand is such that ( x + E F ) ½ 2245 E F ½ . Solution: No Solution yet Problem XIV.2 (10 points) Assuming that an electron under the influence of a drag force starts from rest at t =0, show that the solution of Equation (14-1) is v ( t ) = ( eE τ / m ) [1 - e - t / ]. The drift speed of Eq. (14-2) is the large-time limit of this speed.

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## This homework help was uploaded on 02/05/2008 for the course PHY 251 taught by Professor Rijssenbeek during the Spring '01 term at SUNY Stony Brook.

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homework 11 - phy251_hw11 PHY251 Homework Set 11...

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