Density of electrons = density of Ag atoms 
	    = 10.5 g/cm^3 /107.87 g/mole * 6.022e23 atoms/mole 
	    = 5.87e22 e's/cm^3 = 5.87e28 e's/m^3

Part A) Collision time:
	Tau = m_e/(n e^2 rho) 
	    = 9.1e-31 kg/(5.87e28 e's/m^3 (1.6e-19 coul)^2 1.6e-8 Ohm m
	    = 3.9e-14 sec

Part B)  Electron termal velocity/Mean free path
	V_rms = Sqrt[3 k_B T/m_e]
	      = Sqrt[3 1.38e-23 J/oK 298oK/9.1e-31 kg]
	      = 1.16e5 m/sec
	L = v_rms * tau
	  = 1.16e5 m/sec * 3.9e-14 sec = 4.54e-9 m
	  = 4.54 nm

Part C)
	Lattice spacing = 2.6e-10 m --> 17 lattice spacings

Part B)  First
	Resistivity = rho =Sqrt[2 m E]/(n e^2 L)
	L = Sqrt[2 m E]/ (n e^2 rho)
	  = Sqrt[2 * 9.1e-31 kg * 5.48 eV * 1.6e-19 joules/eV]
	    --------------------------------------------------
	     5.87e28 e's/m^3 * (1.6e-19 coul)^2 *1.6e-8 ohm m
	  = 5.25e-8 m = 52.5 nm
Part A)
	V_f = Sqrt[2 E_f/m_e] = Sqrt[2*5.48*1.6e-19/9.1e-31] = 1.4e6 m/sec
	Tau = L/v_f = 5.25e-8 m /1.4e6 m/sec = 3.8e-14 sec
	   (Note: same collision time as above!!!)
Part C)
	Lattice spacing = 2.6e-10 m --> 202 lattice spacings
	

Part A)
Room temperature * k_B = .024 eV 
Binding energy = 13.6 eV * Z^2 (but Z is reduced by polarizability)
	         = 13.6 eV * (1/12)^2 = .094 eV (Si) = 3.9 * k_b T_room
	         = 13.6 eV * (1/16)^2 = .053 eV (Ge) = 2.2 * k_b T_room
Part B)
Bohr radius = .53e-10 m
	R_Si = .53e-10 * 12 = 6.4e-10 = 2.7 Lattice spacings 
	R_Ge = .53e-10 * 16 = 8.5e-10 = 3.5 Lattice spacings

Part A)
	B = mu_0 n I (where n = turns/m)
	I = B/(n mu_0) = 10 T/(2000/m 4 Pi 1e-7) 
	  = 3979 amps
Part B)
	DF/dl = I B = 3979 amps * 10 T = 4.0e4 N/m

Part A)
	Delta E = 2 mu B = 2 5.79e-5 eV/T 38 T
	        = 4.4e-3 eV
Part B)
	E_gap = 3.53 k T_c = 3.53*8.6e-5 eV/oK 23oK = 7.0e-3 eV