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Unformatted text preview: School of Electrical and Computer Engineering, Cornell University 1 ECE 303: Electromagnetic Fields and Waves Fall 2007 Exam 3 November 15, 2007 INSTRUCTIONS: • Only work done on the blue exam booklets will be graded – do not attach your own sheets to the exam booklets under any circumstances • Every problem must be done in a separate blue booklet – so you must have 3 separate blue booklets before starting the exam • To get partial credit you must show all the relevant work • Correct answers with wrong reasoning will not get points • All questions do not carry equal points • All questions do not have the same level of difficulty DO NOT WRITE IN THIS SPACE School of Electrical and Computer Engineering, Cornell University 2 Problem 1 (40 points) Consider the transmission line circuit shown below: Assume that 3 = l cm, 8 10 3 × = v m/s, and nH 0.1 = L . a) If the source voltage is a step function given by: ( ) ( ) t u t V s 4 = , find and plot the currents ( ) t z I , + , ( ) t z I , − , ( ) t z I , on the transmission line at time v t 2 3 l = . Use the attached sheet to plot your results. Indicate the current values. Partial credit will be given only if proper work is shown. For parts (b) and (c) assume that the source voltage is equal to 4 Volts and it was turned on a very long time ago in the past at time −∞ = t . At time = t , the source voltage is turned off (i.e. it becomes 0 Volts). b) Find the Thevenin equivalent circuit for the circuit on the LEFT of the dashed line, and indicate the values of the Thevenin impedance and the time-dependent Thevenin voltage for times v t l 3 < < . You need to make a sketch of the Thevenin voltage for times v t l 3 < < ....
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This note was uploaded on 02/02/2008 for the course ECE 3030 taught by Professor Rana during the Fall '06 term at Cornell.
- Fall '06