Thevenin’s theorem - Electrotechnology - Exam, Exams of Electrical Engineering

Download Thevenin’s theorem - Electrotechnology - Exam and more Exams Electrical Engineering in PDF only on Docsity! Cork Institute of Technology Higher Certificate in Engineering in Electronic Engineering – Award (NFQ Level 6) Summer 2007 Electrotechnology (Time: 3 Hours) Answer any 5 questions All questions carry equal marks. Examiners: Dr. J. Connell Mr. D. Denieffe Dr. R. O’Dubhghaill Q1. For the circuit shown, calculate: (i) The input current ini . (8 marks) (ii) The voltage at node A (4 marks) (iii) The current in R2 (4 marks) (iv) The voltage across L1 (4 marks) Vac 10V, 2MHz 10Ω 100Ω 56Ω 4.7nF 2.2µH A B iin Q2. (a) State both Thevenin’s and Norton’s theorems. (2 marks) (b) What is the relationship between the Thevenin open circuit voltage and the Norton short circuit current? (2 marks) (c) For the circuit below, use Thevenin’s theorem to calculate the load current.(14 marks) (d) What impedance should replace L1 for maximum power transfer? (2 marks) Q3. (a) Draw a plot of the current versus frequency in a series resonant circuit. (3 marks) (b) Draw a plot of input impedance versus frequency in a parallel resonant circuit. (3 marks) (c) In a series resonant circuit, why do the inductor and capacitor seem to “disappear” at resonance? (2 marks) (d) A parallel resonant circuit consists of a coil, having an inductance of 100µH and a winding resistance of 22Ω, in parallel with a variable capacitor. The resonant circuit is connected to a supply having a frequency of 1MHz. Calculate: (i) The value of C to give resonance. (3 marks) (ii) The dynamic impedance and the Q-factor of the circuit. (3 marks) (iii) The bandwidth of the circuit. (3 marks) (iv) The upper and lower cut off frequencies. (3 marks) VAC 12V 1MHz R1 5.6Ω R2 15Ω C1 4.7nF L1 0.02 mH