EECE 210 Final, Spring 2016

AMERICAN UNIVERSITY OF BEIRUT FACULTY OF ENGINEERING & ARCHITECTURE Name:....................................... FINAL EXAM (EECE210) ELECTRIC CIRCUITS CLOSED BOOK (2 HRS) • Programmable Calculators are not allowed KEY: a c d c c b d a c a c d c d b c a Problem 1 For the circuit shown below, determine the current I0 for R=2 KΩ a. 3.8 mA b. 4.444 mA c. 4.692 mA d. 4.824 mA e. None of the above Problem 2 Determine the current in the 8Ω resistor for R=4Ω a. 0.13 A b. 0.15 A c. 0.2 A d. 0.1875 A e. 0.678 A R Problem 3 Determine the voltage v(t) for t ≥ 0 for R = 8Ω. a. volts 2e 6 )t( v −6t + = b. volts 4e 6 )t( v −6t + = c. volts 6e 6 )t( v −6t + = d. volts 9e 6 )t( v −6t + = e. None of the above Problem 4 Determine the total capacitance for the following circuit a. 10 µF b. 6 µF c. 5 µF d. 3 µF e. None of the above R Problem 5 Find the Thévenin resistance with respect to the terminals a, b for the circuit shown below. a) 37.5 Ω b) 9.375 Ω c) 18.75 Ω d) 26.5 Ω e) None of the above Problem 6 If Vs = 5 mV in the circuit shown below, find Vo. Assume that the op-amp is ideal and operating in the linear region. a) 5.45V b) 1.36 V c) 4.09 V d) 2.72 V e) None of the above Problem 7 Determine the power supplied by the independent current source in the circuit shown below given that Is = 2 mA. a) 3.15 mW b) 5.60 mW c) 8.75 mW d) 1.40 mW e) None of the above Problem 8 The switch in the circuit shown below has been opened for a very long time before it is closed at t = 0. It is known that t d d C t e B t B t v α ω ω − + = ) sin cos ( ( ) 2 1 for t ≥ 0 . Find B2. a) 50 V b) 200 V c) 100 V d) 150 V e) None of the above Problem 9 Find Vo in the circuit shown below. a) 0.48 + j9.36 V b) -1.12 + j8.16 V c) -2.72 + j6.96 V d) 2.08 + j10.56 V e) None of the above Problem 10 The two switches have been closed for a long time. They are opened at t=0. Find vC(t) in V for t > 0 if V1 = 27V. a) 36 t e-t + 12 e-t b) 24 t e-t + 8 e-t c) 12 e-t + 8 e-2t d) 48 t e-t + 16 e-t e) None of the above + VC - V1 Problem 11 The switch has been closed for a long time. It is opened at t=0. Find iL(t) in A If I = 4A. a) 2(2 – e-4t) b) 4(2 – e-4t) c) (2 – e-4t) d) (1 – e-4t) e) None of the above Problem 12 The switch has been closed for a long time. It is opened at t=0. Find i(t) in A If L = 4H. a) 1 – 0.137 e-47.91t + 3.087 e-1.37t b) 1 – 0.137 e-47.91t + 3.137 e-2.09t c) 1 – 0.087 e-48.63t + 3.087 e-1.37t d) 1 – 0.319 e-45.62t + 3.319 e-4.38t e) None of the above iL I L Problem 13 Find the thévenin equivalent voltage seen by the load if v(t) = 10cos(1000t +30°) (V). a) vTH(t) = 23.21cos(1000t + 18.2°) (V). b) vTH(t) = 13.93 cos(1000t + 18.2°) (V). c) vTH(t) = 9.29 cos(1000t + 8.2°) (V). d) vTH(t) = 13.93 cos(1000t - 1.8°) (V). e) None of the above Problem 14 Find the value of the inductor L2 such that the equivalent impedance as seen from terminals a and b is purely resistive. Given L1=20mH a b + - 10mH 2mF 100cos(100t+30) 5mF L1 L2 10Ω 100cos(100t+30) 10Ω 2mF 1Ω a) 10 mH b) 50 mH c) 40 mH d) 5 mH e) None of the above 50µF V(t) 200 Ω Problem 15 In the circuit shown below, find the voltage vab if B=0.5 A/V. 40Ω 20V 60Ω BVx + Vx - 5Ω + Vab - a 15Ω 2Ω 3Ω b 20Ω 10Ω a. 12V b. -30V c. 30V d. -12V e. None of the above Problem 16 The initial voltage across the capacitors are V1=30V and V2=10V respectively. Find the expression of vc (t) for t 0 if R= 8kΩ. a) vc(t)= 4e-2500t+16 V b) vc(t)= 5e-2500t+15 V c) vc(t)=16e-2500t+14 V d) vc(t)=15e-4000t-5 V e) None of the above Problem 17 If i(t)=4 cos (400t+90°). Find i0(t) in A a. 2.774cos(400t+109.4°) b. 3.673cos(400t+60°) c. 6.476cos(400t+88.4°) d. 2.91cos(400t+70°) e. None of the above