TAILIEUCHUNG - Electromagnetic Field Theory: A Problem Solving Approach Part 69

Electromagnetic Field Theory: A Problem Solving Approach Part 69. Electromagnetic field theory is often the least popular course in the electrical engineering curriculum. Heavy reliance on vector and integral calculus can obscure physical phenomena so that the student becomes bogged down in the mathematics and loses sight of the applications. This book instills problem solving confidence by teaching through the use of a large number of worked problems. To keep the subject exciting, many of these problems are based on physical processes, devices, and models. This text is an introductory treatment on the junior level for a two-semester electrical engineering. | Problems 655 -------------- 1 Cy Ty---------------------- ---- 2 c2 2------------ Section 8-3 16. A transmission line is excited by a voltage source Vo cos tot at z I. The transmission line is loaded with a purely reactive load with impedance jX at z 0. a Find the voltage and current distribution along the line. b Find an expression for the resonant frequencies of the system if the load is capacitive or inductive. What is the solution if X Zo c Repeat a and b if the transmission line is excited by a current source Io cos at at z 1. 17. a Find the resistance and conductance per unit lengths for a coaxial cable whose dielectric has a small Ohmic conductivity a and walls have a large conductivity a Hint The skin depth 8 is much smaller than the radii or thickness of either conductor. b What is the decay rate of the fields due to the losses c If the dielectric is lossless r 0 with a fixed value of 656 Guided Electromagnetic Waves outer radius b what value of inner radius a will minimize the decay rate Hint 1 l ln . 18. A transmission line of length I is loaded by a resistor RL. a Find the voltage and current distributions along the line. b Reduce the solutions of a when the line is much shorter than a wavelength. c Find the approximate equivalent circuits in the long wavelength limit fc 1 when RL is very small RL Zn and when it is very large RL Za . Section 8-4 19. For the transmission line shown Zo 50 JZi 100 1- z 0 X 4 a Find the values of lumped reactive admittance Y jB and non-zero source resistance Rs that maximizes the power delivered by the source. Hint Do not use the Smith chart. b What is the time-average power dissipated in the load 20. a Find the time-average power delivered by the source for the transmission line system shown when the switch is open or closed. Hint Do not use the Smith chart. 400 wv A 4 A 4 Vocosûjî Zo 100 Zo 50 Rl 100 R 25 b For each switch position what is the time average power dissipated in the load resistor RL Problems 657 c For

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