1 EET 3104 – ELEMENTS OF ELECTRICITY AND ELECTRONICS ASSIGNMENT # 5 Due: 11:59 P.M. on March 30, 2017 Name: Assignment (100 points) (1) Read the following before answering the questions a. Read the syllabus. b. Watch the videos for Lecture 15 and 18 c. Read the Lecture notes 15 to 18 (2) Answer all questions on the following pages. When answering numerical clearly write all the steps and formulas used along with units. (3) Points for each question is indicated next to it. Question 1 (10 points) (each bit carries equal points) State true or false (a) Direction of magnetic flux can be found by using right hand rule. (b) Unit of inductance is Henry. (c) Faraday’s laws of electromagnetic induction states that whenever a conductor cuts magnetic flux, an e.m.f. is induced in that conductor. (d) Time constant of a resistor and inductor series circuit is given by the equation = . (e) Time period of a sinusoidal waveform is the time taken to compete one cycle. (f) The frequency of typical AC supply in united states is 50 Hz. (g) The voltage across and current through a resistor are in phase. (h) The current through a pure inductor lags the voltage across it by an angle of 900 . (i) The current through a pure capacitor leads the voltage across it by an angle of 900 . (j) Power factor is the cosine of the angle between the voltage and current. 2 Question 2 (10 points) For the circuit shown below (a) Determine the time constant () (2 points) (b) Write the mathematical expression for the current and voltage . (2 points) (c) Determine at 3 time constant. (3 points) (d) Determine at 3 time constant. (3 points) E 20V L 300mH R 1 20k? S + – iL vL 3 Question 3 (10 points) (a) Find the instantaneous current at 6 ms after the switch is closed for the given circuit. (5 points) (b) Find the instantaneous voltage across the inductor for the circuit shown in part (a) at time 6 ms after the switch is closed. (5 points) 4 Question 4 (10 points) a) Find the total inductance for the network shown below. (5 points) b) Reduce the network to the fewest elements. (5 points) L1 47mH L2 10mH L3 30mH L4 22mH LT L1 30mH L2 30mH L3 30mH L4 30mH C1 1µF C2 1µF 5 Question 5 (a) Find the time period of the periodic waveform with a frequency 60 Hz and 1000 Hz (4 points) (b) Find the maximum (peak) value and frequency of the following waves. (6 points) (i) 20 sin (377t) (ii) 12 sin (2 × 120 t) (iii) 106 sin 10,000 6 Question 6 a) Find instantaneous value of the voltage for a 50 sine wave when = 10 at time of 10 . (5 points) b) Develop an expression for the instantaneous value of a sine wave voltage where peak value of the voltage is 150 V and frequency is 60. (5 points) Question 7 (10 points) Find the average and rms value of the following sinusoidal wave forms. (i) = 120 sin 377 (ii) = 6 sin 2 × 100 7 Question 8 (10 points) For the given waveforms A and B determine the phase shift between them in degrees. Considering A as reference determine whether waveform B is leading or lagging A. (a) (b) (c) (d) 8 Question 9 (10 points) (a) The voltage across a 3 ? resistor is as given below. Find the sinusoidal expression for the current (5 points) (i) = 150 sin 200 (ii) = 30 sin( 377 + 200 ) (b) Determine the inductive reactance (in Ohms) of a 2 mH coil for the frequencies given below. (5 points) (i) 60 Hz (ii) 4 kHz 9 Question 10 (10 points) (a) The voltage across a 5 mH coil is = 120 sin 20. What is the sinusoidal expression for the current? ( 3 points) (b) Determine the capacitive reactance (in Ohms) of a 5 capacitor for the following frequencies. ( 4 points) (i) 60 Hz (ii) 2 kHz (c) The voltage across a 1 capacitor is = 30 sin 200. What is the sinusoidal expression for current. (3 points)