Old Midterm Exam Questions - Basic Circuit Theory - Fall 1994 | ENEE 204, Exams of Electrical and Electronics Engineering

Download Old Midterm Exam Questions - Basic Circuit Theory - Fall 1994 | ENEE 204 and more Exams Electrical and Electronics Engineering in PDF only on Docsity! ENEE 204 MIDTERM EXAM I March 8, 1994 Problem 1 (25 points) A. What is an inductor? Draw the terminal representation, complete with reference directions. B. Define Inductance. Define all quantities that you write down. C. What is the MKSA unit for inductance and how is it related to Ohms? D. What is the terminal relationship for an inductor? E. What is the continuity equation for an inductor? From what principle is it derived? F. What is the relationship between the peak voltage and peak current of an inductor when a sinusoidal signal is applied? Problem 2 (25 points) Consider describe the circuit shown below. A. How many independent KVL and KCL equations are there? B. Find the complete system of first-order differential equations. Clearly indicate the reference directions, KCL equations, KVL equations, and terminal relationships used in the process. Let iR1 be the current through R1, etc. Problem 3 (25 points) A. The current through a 47 µF capacitor is given by i(t) = 5x10-3 sin (2000t) A. What is the peak voltage across the device? B. What is the phasor representation of the sinusoidal current i(t) = 4x105 cos (7ωt+¾) A. C. Write the voltage v(t) in the standard form [Vm cos (ωt+φv)] if the phasor representation is 55ˆ jV +−= µV. D. A voltage v(t) = 75 cos ( 100t + π/3 ) mV is fed across a two terminal device with an admittance Y = 1 - j 3 . Find the expression for the time dependence of the AC current flowing through the device. E. The impedance of a branch element is given by Z = 11 5+ j kΩ. Find the reactance, admittance, and susceptance of the element. Problem 4 (25 points) Consider describe the circuit shown below. A. Draw the steady-state version of the circuit showing impedances and phasors. B. Use the superposition principle to find the phasor current $I o . Bonus Problem (10 points) Find the input admittance of the figure shown below. You must show your work and explain clearly any assumptions you make. Note that all branches have the identical impedance. C1 C2 C3 R1 R2 R3 is(t) 1Ω 1Ω 3Ω 7Ω 3Ω 1Ω 1F 1H io i t t A( ) cos( )= 5 2 v t t V( ) cos( )= 15 2 Z Z Z Z Z Z Z Z Z Z ZZ YT--> ENEE 204 MIDTERM EXAM II April 21, 1994 Problem 1 (25 points) Consider the circuit shown below. Find the equivalent (a) input impedance, (b) Thevenin circuit and (c) Norton circuit at the a - b terminals indicated. Clearly label all of your work. Voltage is in V; current in A. Problem 2 (25 points) Consider the circuit shown below. All voltages are in V, all currents are in A. (a) Draw the phasor-equivalent circuit so that it is consistent with the general mesh analysis formalism. Clearly indicate the all circulating mesh currents. (b) Write down, but do not solve the general mesh equations in matrix form. Problem 3 (25 points) Consider the circuit shown below. (a) Write the matrix form for the general node analysis problem. (b) Find the value of the resistance R that results in a voltage of 3 V across the 2 Ω resistor. Problem 4 (25 points) Consider the circuit shown below. (a) Draw the circuit for t<0 and find the relevant initial conditions. (b) Draw the circuit for t>0 and find the differential equation for the current through the inductor. (c) Find the solution for the inductor current for t>0. Plot the power through the inductor over a relevant time period. a b 3 Ω 3 Ω 6 Ω 6 Ω sin(ωt)18cos(ωt) 3 Ω 5 Ω 1 Ω 1 Ω 1 Ω 3 Ω 3 Ω 3cos(5t) 1 H 2 H 0.2 F 1 Ω 3sin(5t) co s( 5t ) si n( 5t ) 21/2cos(5t-45o) 7 Ω 1 Ω 0.2 Ω 2 Ω1 Ω R (Ω) 2 A 6 A 10 V t=0 t=0 10 V 10 Ω 20 Ω 10 Ω1 µH