EE1111 Lab Manual-Diploma - Lab 2

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Jan 9, 2024

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

Contents Lab Experiment 2: Series and Parallel Circuits ....................................................... 1 Aims of this experiment ............................................................................................................ 1 Videos and guides for review .................................................................................................... 1 Lab 2: Part A. Pre-Lab Work ...................................................................................................... 2 Lab 2: Part B. Hardware Explanation ........................................................................................ 2 Lab work 2 procedure ............................................................................................................... 5 Required components ............................................................................................................ 5 Series and parallel connections ............................................................................................. 5 i

Lab Experiment 2: Series and Parallel Circuits Aims of this experiment The aim of this lab experiment is as follows: 1 Study the properties of series and parallel combination of resistors. 1 Validate voltage and current division laws. Videos and guides for review List of suggested videos : Prototyping board Breadboard Review (New) Introduction to the power supply Power Supply Review (New) Introduction to the multimeter Multimeter Review (New) Measuring voltage with a multimeter Measuring current with a multimeter List of suggested guides from Appendix:  Prototyping board (Breadboard)  DC power supply  Digital multimeter Page 1

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Lab 2: Part A. Pre-Lab Work Make sure you complete the online quiz for Lab 2 before attending your session. Note that this quiz can be found in Moodle in the Laboratory section. Lab 2: Part B. Hardware Explanation Please complete all the tasks given in this section during the lab session. Do not forget to watch the related lab videos and guides that are suggested for this lab experiment. 1. Annotate the diagram in Figure 2.1, on the next page, to show how you would set up the circuit in Figure 2.1 if you were in the lab. Assume that we wish to measure the current through the light bulb A for this experiment. You may copy the image in Figure 2.12 into MS Paint, add your annotations, and then copy the annotated image back into this document. Refer to the Preface section in the Online Lab Manual for an example annotated image. The annotation in Figure 2.1 must show:  The components on the picture of the breadboard (in a dark blue colour)  Connections on the picture of the breadboard in red or black (or any other relevant colour) depending on the colour of the cable or wire insulation that you would use in a lab.  The cable connections between each piece of equipment and the breadboard and/or the components on the breadboard. Also, be prepared to explain to the lab demonstrator what connection type you would use at each end of the cable (i.e. banana plug, BNC, alligator clamp, etc.). It may be helpful to add text descriptions of this to your diagram. Figure 2.1: The simple circuit with lightbulb and DC power supply for Lab work 2. Some helpful tips with this exercise are:  Ensure that annotated lines are thick enough to be easily seen, but not too thick that it becomes difficult to see what breadboard holes you are connecting wires to.  Ensure that you understand why you have connected equipment in the particular configuration as lab demonstrators may ask you this question. 2

Figure 2.2: Part B. Equipment diagram for annotation exercise. Page 3

2. Explain how you would set up the DC power supply and multimeter in the following Answer Box. For the dc power supply, include explanations on how you would set up:  Channel 1 voltage and current settings  The series/parallel buttons in the dc power supply (explain why this setting is important or not important for your experimental setup)  The Power button and ON/OFF button (what pressing these buttons do and when they should be pressed) For the multimeter, include an explanation on how you would set up:  Current measurement (What buttons are required? Should you press the DCV, ACV, Ω, DCA, ACA or the DC+AC button and why?)  How would you set the scale of the current measurement? Page 4

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Lab work 2 procedure Please complete all the tasks given in this section during the lab session, please do not forget to watch the related lab videos and guides that are suggested for this lab experiment on page 1 . Required components In this experiment you will be required to use the following components:  Your breadboard.  Miniature lightbulbs.  220 Ω resistor. Series and parallel connections 1 Connect a lightbulb to the DC power supply as show in Figure 2 .3(a). Start with V S = 2 V and measure the voltage across lightbulb A and the current through it using the digital multimeter. Increase the voltage at increments of 2 V up to maximum of 10 V , and for each voltage measure the current through the lightbulb. Record all your measurements in the following Table, and then calculate the resistance of the lightbulb for each set of measured voltage and current. (a) (b) (c) Figure 2.3: The simple circuits with lightbulb and DC power supply for Lab work 2 procedure: (a) A single lightbulb, (b) two series lightbulbs, and (c) two parallel lightbulbs. Voltage Current Resistance V S = 2 V 0.0417A 47.96ohms V S = 4 V 0.0833A 48.02ohms V S = 6 V 0.125A 48.00ohms V S = 8 V 0.167A 47.90ohms V S = 10 V 0.208A 48.08ohms 5

2 Repeat the previous experiment with 220 Ω resistor instead of lightbulb A in Figure 2 .3(a). Record all your measurements in the following Table, and then calculate the resistance for each set of measured voltage and current. Voltage Current Resistance V S = 2 V 0.00909A 220.02 ohms V S = 4 V 0.0182A 219.78 ohms V S = 6 V 0.0273A 219.78 ohms V S = 8 V 0.0364A 219.78 ohms V S = 10 V 0.0455A 219.78 ohms 3 Sketch the i - v curves of the lightbulb and the resistor together in the place provided below and explain your observation in terms of the behaviour of both lightbulb and resistor under different voltages and currents, particularly for the resistance of lightbulb. Does it remain constant? Why? Almost unchanged. Because resistance is a property of the conductor itself, it is related to the length and cross- sectional area of the conductor. And the power supply voltage does not exceed the rated voltage of the lightbulb and resistor. 6

4 Build the circuits shown in Figure 2 .3(b) and Figure 2 .3(c) side-by-side on your breadboard and apply 12 V ( V S = 12 V ). Observe the brightness of the lightbulbs B , C , D , and E , and make comparisons between their brightness by adequately describing what you mean in your comparison, i.e., use the adjective such as “ the same brightness as ”, “ brighter than ”, “ dimmer than ”, and so on. Provide all necessary explanations to justify your comparison. First, the same brightness as B and C. Second, the same brightness as D and E. However, D and E brighter than B and C. Because the brightness of the lightbulb depends on the power of the lightbulb. And the voltage of the series circuit is half of the parallel circuit. In the case of constant resistance, according to I = U / R. It can be concluded that the current of the series circuit is also half of the parallel circuit, and finally P = U * I. It can be known that the power of the lightbulb in the series circuit is a quarter of that of the parallel circuit. So, D and E brighter than B and C. 5 Based on your observations from previous results, which electrical parameter impacts the brightness? Use your measurements in the Table of question 1 and calculate the values of that parameter to justify your reasoning. Voltage will impact the brightness. 6 In the circuit of Figure 2 .3(b), increase the applied voltage to 24 V while keeping the applied voltage in the circuit of circuit of Figure 2 .3(c) at 12 V . Now compare the brightness of lightbulbs ( B , C ) with ( D , E ). Record your observations and reasoning (provide any necessary explanation to justify your reasoning by collecting relevant measurements and numerical values for electrical parameter impacting the brightness of each lightbulb) The same brightness as B, C, D and E. Because the total voltage of the series circuit is increased from 12V to 24V. Then the voltage of each of the 4 lightbulbs is equal, because the resistance of the lightbulbs is equal. So, the current of the series circuit lightbulb has doubled. So, the power is the same. Then brightness is also same. 7

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7 Now build the circuits given in Figure 2 .4 and set the power supply to 12 V ( V S = 12 V ). Compare the brightness of the lightbulbs in these two circuits with the ones in Figure 2 .3(b) and Figure 2 .3(c). The same brightness as 2.4(b) and 2.3(c). (a) (b) Figure 2.4: The simple circuits with lightbulb and DC power supply for Lab work 2 procedure: (a) Three series lightbulb and (b) three parallel lightbulbs. 8 What happens to the overall resistance connected to the power supply as you add more lightbulbs in series ? How does it impact the brightness of the lightbulbs? What happens to the current through supplied by the power source as you add more lightbulbs in series ? If I series more lightbulbs, the total resistance of the power supply will increase as the number of lightbulbs increases. The brightness of the lightbulbs will dim. The voltage decreases and the resistance of each lightbulb does not change, then the current will decrease. 9 What happens to the overall resistance connected to the power source as you add more lightbulbs in parallel ? How does it impact the brightness of the lightbulbs? What happens to the current through supplied by the power source as you add more lightbulbs in parallel ? With more lightbulbs in parallel, the total resistance of the circuit will decrease. Due to the parallel circuit, the voltage on each branch is equal, so the brightness of the lightbulb remains unchanged. The current of the total circuit will increase. 10 Can you add unlimited number of bulbs in parallel? Why? In theory, an unlimited number of lightbulbs can be added. But it is not actually possible. Because of the total circuit cannot provide unlimited power and current. 8

11 Explain why all the wirings in buildings are done in parallel. Because in the parallel circuit, it can ensure that the electrical appliances have enough voltage to support the work. Lab work 2 Date: Assessor name and signature: Mark: --- End of Lab Experiment 2 - 9