EE1111 Lab Manual-Diploma - Lab 7

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Jan 9, 2024

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Diploma Program Course EE1111 LABORATORY MANUAL #7 Electrical and Telecommunications Engineering School of Electrical Engineering and Telecommunications Student Name: …………………… Student ID: …………………………

Contents Lab Experiment 7: AC Circuits .............................................................................. 2 Aims of this experiment ............................................................................................................ 2 Videos and guides for review .................................................................................................... 2 Lab 7: Pre-Lab work .................................................................................................................. 2 Lab 7: Part B. Hardware Explanation ........................................................................................ 3 Lab 7: Part C. Simulation and Discussion of AC Circuits ............................................................ 4 Required components ............................................................................................................ 4 I. Frequency/Phasor domain analysis of AC circuits ............................................................ 4 II. Maximum average power transfer ............................................................................... 7 Page i

Lab Experiment 7: AC Circuits Aims of this experiment The first aim of this lab experiment is to investigate the following concepts in AC circuits: 1 Frequency-dependent behaviour of RC circuits. 2 RMS value of AC signals. 3 Maximum average power transfer Videos and guides for review List of suggested videos : Power supply Signal generator Oscilloscope Multimeter List of suggested guides from Appendix:  Power supply  Signal/Function generator  Oscilloscope  Digital multimeter Lab 7: Pre-Lab work Make sure you complete the online quiz for Lab 7 before attending your session. Note that this quiz can be found in Moodle in the Laboratory section. Lab 7: Part B. Hardware Explanation Do not forget to watch the related lab videos and guides that are suggested for this lab experiment for this part of the laboratory. Page ii

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1. Explain how you would set up the multimeter to measure RMS voltage or RMS current in the following Answer Box. Write this as a set of sequential instructions. (10 marks) Page 3 RMS Current Step 1: turn on the power button and press ac amp(ACA) tab to measure AC current and also use auto/man tab to adjust the desired range. Step 2: Plug a red banana cable into the middle red port marked 2A and Plug a black banana cable into the black port marked with a ground symbol. Step 3 : Connect the red cable to the circuit. RMS Voltage Step 1: turn on the power button and press ac amp(ACV) tab to measure AC voltage and also use auto/man tab to adjust the desired range. Step 2: Plug a red banana cable into the red topmost port marked V - Ω and Plug a black banana cable into the black port marked with a ground symbol. Step 3 : Connect the red cable to the circuit.

AC Circuits Lab 7: Part C. Simulation and Discussion of AC Circuits For this section, you will use Autodesk Circuits in TinkerCAD to build and test the circuits for each question. IMPORTANT : For each Answer Box, show pictures of the circuit that you have used in Circuits in TinkerCAD. Make sure that you include the multimeter/oscilloscope readout in the picture when finding the voltage and current. Required components In this experiment you will be required to use the following components:  Your breadboard.  1 kΩ resistor.  100 nF capacitor.  10 mH inductor. I. Frequency/Phasor domain analysis of AC circuits 1 Construct the RC circuit of Figure 7.1 on your breadboard. Use the signal generator to provide a 10 V peak-to-peak sinusoidal with a frequency of 100 Hz . Use oscilloscopes to measure the input voltage v ¿ and the output voltage v out . Show these waveforms in the Answer Box below with 2 full periods of each signal. Comment on the amplitude of the input voltage v ¿ and the output voltage v out . Note that Autodesk Circuits on TinkerCAD cannot trigger both oscilloscopes at the same time. Hence, draw what the two voltage waveforms should look like when they are triggered together on the graph in the Answer Box (HINT: Think about phase shifting of waveform v out with respect to due to v ¿ due to the capacitive reactance and look at your pre-lab calculation of the phasor phase-shift angle for v out with this circuit). (10 marks) Figure 7.1: RC circuit for frequency/phasor domain analysis. Page 4

1 Also explain any potential discrepancy or difference between simulated and practical measured output voltages for this circuit. (6 marks) 2 Increase the frequency of the signal generator according to the Table below and repeat the measurements looking at the effect on the output waveform. (10 marks) Page 5 time shift is 86.405 degree Wire and other component all have resistor in real life, so Vout would small than idea Vout.

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AC Circuits Frequency Output voltage magnitude | V out | (peak-to-peak) Frequency Output voltage magnitude | V out | (peak-to-peak) 0 Hz 10V 1.6 kHz 7V 100 Hz 10V 2 kHz 6V 400 Hz 10V 2.4 kHz 5.6V 800 Hz 9V 2.8 kHz 5V 1.2 kHz 8V 3 kHz 4.5V 3 Explain why the output voltage waveform is changing as frequency increases, particularly the magnitude. What happens to the phase-shift angle as frequency increases? What would be one possible practical application of such a circuit based on your observations? (10 marks) 4 1. The effective value of the voltage of the periodic function is inversely proportional to the amplitude according to the formula. 5 2. The change in phase angle is 90°, a quarter cycle. 6 3. High-pass filter. 7 Use your measurements in question 2 to graph the ratio of output voltage magnitude to input voltage magnitude | V out | / | V ¿ | vs the frequency in Excel . Find an approximate frequency at which the ratio reaches 1 / √ 2 (or 70.71%) of the maximum value, and label it on the graph. This frequency is known as cut-off frequency f c . Think about whether frequency or the output voltage/input voltage ratio should be on the x - axis here. Add appropriate labels, title and scaling (14 marks) Frequency should be on x-axis Page 6

II. Maximum average power transfer 8 Consider the AC circuit shown in Figure 7.2, where an inductive load is connected to the output terminals a and b . The inductive load has an unknown load resistance R L and inductance of L = 10 mH . Calculate the value of R L and the source frequency in Hertz such that the circuit can deliver maximum average power to the inductive load. Then calculate the maximum average power P max . Note that this question does not need Autodesk Circuits on TinkerCAD. (10 marks) Note that the voltage source value is given in peak-to-peak , but you need the magnitude for average power calculation. Figure 7.2: AC circuit with inductive load to examine maximum average power transfer. Z_c = 1 / (100nF * j * 2 * pi *f) ohms Z_R = 1k ohms Z_th = 1000 + 1 / (100nF * j * 2 * pi *w) ohms Z_L = 10mH * j * 2 * pi *f ohms Z_L_total = 10mH * j * 2 * pi *f + R_L ohms When Z_L_total = Z_total, P get maximum value So 10mH * j * 2 * pi *f + R_L = 1000 - j / (100nF * 2 * pi *f)  R_L = 1000, f = 10^(9/2) / 2 * pi = 5032.92 Hz So P_max = 3.125mW 9 For the AC circuit of Figure 7.2, how would you measure the average output power across terminals a and b ? What equipment would you use? (10 marks) Page 7

AC Circuits Measure the rms current and voltage through the terminals a and b by multimeter. Due to it wanna average output power, it can use i_rms * v_rms to find average output power. Lab work 7 Date: Assessor name and signature: Mark: Page 8

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