ECE495N-F08-Exam_1_practice_solution

ECE495N-F08-Exam_1_practice_solution - 1 ECE 495N PRACTICE...

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1 ECE 495N PRACTICE EXAM I CLOSED BOOK, Sept. 25, 2007 Problem 1 [p. 2,] 8 points Problem 2 [p. 3] 8 points Problem 3 [p. 4] 9 points Total 25 points Problem 1 (a) 5 points 1000 K 300 K μ E D(E) 1 2 Source Channel Drain A channel has a density of states as shown, namely a constant non-zero value for E 0 and zero for E < 0, that is, D ( E ) = D 0 ϑ ( E ), where represents the unit step function. It is connected to two contacts with the same electrochemical potential μ whjich is ~ 0. Is there a current in the external circuit ? If so, is it in the direction shown (from the hot to the cold contact) or opposite to the direction shown (from the cold to the hot contact)? Explain your reasoning. Inside the channel Electrons flow from hot to cold above μ, and from cold to hot below μ. D(E) is higher for energies above μ than for energies below μ. Hence net flow of electrons is from hot to cold. In external circuit Electrons flow from cold to hot. Current flows from hot to cold.
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2 External current will be in the direction shown.
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This note was uploaded on 12/30/2010 for the course ECE 495N taught by Professor S.datta during the Spring '08 term at Indiana University-Purdue University Fort Wayne.

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ECE495N-F08-Exam_1_practice_solution - 1 ECE 495N PRACTICE...

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