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Lab report (eee230)   experiment 7

Lab report (eee230) experiment 7






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    Lab report (eee230)   experiment 7 Lab report (eee230) experiment 7 Document Transcript

    • FACULTY OF ELECTRICAL ENGINEERING ELECTRICAL ENGINEERING LABORATORY 1 (EEE230) LAB REPORT Lab Report No. 6 Experiment No. 7 Title Series Resistor-Capacitor Circuit Date Performed 15 / 8 / 2013 Date Due 22 / 8 / 2013 Date submitted 22 / 8 / 2013 Working days late: ____________ equates to ____________% reduction at 5% per day Prepared by: NAME UiTM NO. GROUP MOHD NORHAIDIE BIN ROSLI 2012605084 EE1113J NUR YASMINE BINTI ABDUL SAMAT 2012218936 EE1113J NURUL NUR BINTI NOR AZMI 2012235954 EE1113J Assessment: ASSESSMENT MARKS Report Format / 5 Introduction / Theory / 15 Results / 30 Discussion / Questions / 25 Conclusion / 20 References / 5 Total Marks / 100 Final Marks after Penalty / 100 Lecturers Name ROSZITAIDA BINTI ADZEMIN Feedback Comment ................................................................................................................................................... Report submission slip (Student’s copy) Students: 1. Mohd Norhaidie Bin Rosli 2. Nur Yasmine Binti Abdul Samat 3. Nurul Nur Binti Nor Azmi Expt No. & Title: 7 & Series Resistor-Capacitor Circuit (Signature & Stamp) Date:
    • 2 TABLE OF CONTENTS Section Page Objectives 3 List of Requirements 3 Theory 4 Procedure 6 Results 8 Questions / Discussion 10 Conclusion 11 References 12
    • 3 EXPERIMENT 7 SERIES RESISTOR-CAPACITOR CIRCUIT OBJECTIVES The main purposes of this experiment are: 1. To understand the relationship between voltage, current and phase angle. 2. To calculate the phase angle. LIST OF REQUIREMENTS The equipments that are used in this experiment are listed as below: 1. Signal generator 2. Oscilloscope The components that are used in this experiment are listed as below: 1. Decade capacitor box 2. 1 kΩ resistor
    • 4 THEORY Figure 7.1 shows a resistor and a capacitor connected in series supplied with an alternating sine wave voltage. Let the current flowing in the circuit given by the equation 7.1. (7.1) Using Ohm’s Law the voltage across the resistor is (7.2) Hence, (7.3) (7.4) where (7.5) (7.6) From equations 7.1 and 7.4, as and , it can be seen that the voltage across R and current flow through it are in phase (same phase). The shape of and waveforms are as depicted in Figure 7.2. If the voltage and current equations are written in phasor notation, then VR = VR < 0° where the magnitudes of VR and I are root mean square (rms) values. The phasor diagrams for VR and I are as in Figure 7.3 which shows that they are in phase. The voltage across capacitor VC can be derived from (7.7) (7.8) (7.9) (7.10) (7.11) (7.12) XC is known as the capacitive reactance.
    • 5 From Equation 7.1 and 7.11 it can be seen that the voltage across capacitor lags the current by 90°. In phasor notation, the voltage and the current can be written as VC = VC√-90° and I = I√0° respectively. Figure 7.4 and 7.5 show the waveforms and the phasor diagram for C and I. The waveforms and the complete phasor diagram for the circuit in Figure 1 are illustrated in Figure 7.6 and Figure 7.7. Figure 7.6 is obtained by combining Figure 7.2 and Figure 7.4 while combination of Figure 7.3 and Figure 7.5 results in phasor diagram shown in Figure 7.7. The angle between the voltage and the current is called phase angle. In Figure 7.7 this angle is denoted by θ. From the figure, the magnitude of the voltage is given by: (7.13) (7.14) (7.15) (7.16) The phase angle is given by (7.17) (7.18) For a.c. circuits, the resistance is termed impedance and is given the symbol Z. The magnitude of impedance of a circuit containing a series combination of a resistor and a capacitor is given . Thus, the impedance for the circuit of Figure 7.1 is (7.19) With phase angle of (7.20) In phasor notation, this is written as (7.21)
    • 6 PROCEDURE 1. The circuit as in Figure 7.8 is connected. 2. The V and VR are obtained on the oscilloscope. The waveforms is drawn and labelled completely. The peak values of V and VR are stated. For the circuit, the current is in phase with the voltage VR. Thus, the phase difference between V and VR is equal to the phase angle between V and I waveforms. Determine the distance between the waves (d1) and the distance for one cycle (X1). 3. The position of resistor and capacitor is changed and the V and VC waveforms are obtained. The distance between the waves (d2) and the distance for one cycle (X2) are determined. 4. All the readings are recorded in Table 7.1.
    • 7 RESULTS C1 = 0.187 µF C2 = 0.085 µF V 9.8V 9.8V VR 7.6V 4.8V VC 6.4V 8.8V d1 2 2.5 X1 20 20 d2 2.5 1.5 X2 20 20 C1 = 0.187 µF C2 = 0.085 µF Calculated phase angle 40.40° 61.89° Measured phase angle θ1 40.10° 61.38° θ2 36° 45° θ3 45° 63°
    • 8
    • 9 DISCUSSION 1) From this experiment, we have to understand the relationship between voltages, current and phase angle. We have to understand the relationship from a simple circuit that consist only voltage source, resistor and capacitor respectively. The voltage supply is in alternating sine wave. For the component that we use is decade capacitor box and 1 kΩ resistor. The value of voltage across the resistor can be determined by using Ohm’s Law. Ohm’s Law:- But from this experiment, we use equipment to measure the voltage across the resistor and the capacitor. The value of output voltage will be show at oscilloscope. Oscilloscope will be the equipment to measure the voltage. The oscilloscope will be use two probe. First probe will use to measure the voltage across resistor and the second probe will use to measure the voltage across capacitor. We determine the two voltage value and the phase different by this two probe us using. Based on the result obtain, the value that we are measure is have slightly different with the value that we calculated. There must be having a faulty in a component, the equipment or error when doing this experiment. The value of VC of C1 and C2 is nearly approximate. It is because the value of capacitor C1 is bigger than C2. The value of calculated phase angle and measure phase angle is also slightly different. The value of phase angle is depending on the value of voltage that we measure. Phase angle have relationship with the voltage. If the value of voltage is changing, then the phase angle also will change. It also depends on the value of distance between the waves and distance for one cycle. 2) The factor that contributes to errors that we observe in the readings which are parallax error and the value is not approximate because the analog function generator. 3) For the parallax error, we must see the scale with eyes perpendicular to the scale. We must make sure that ours is directly perpendicular to the scale. For the analog function generator, we just have to change the analog function generator to digital function generator.
    • 10 CONCLUSION 1. For any value of R and C, can we determine the phase angle between VR and VC? What are the values of these angles? Yes, we can actually determine the phase angle between VR and VC by using this formula: In order to gain the value of VR and VC, we need to find the value of R and C first by using these formulae: Hence, the answer is 85.58° for C1 and 87.33° for C2. 2. What will happen to the phase angle if the value of C: a) increases and b) decreases? What happens instead if the value of C is fixed and the value of R is changed? a) If the value of C increases, then the phase angle becomes smaller. b) If the value of C decreases, then the phase angle becomes larger. However, if the value of C fixed and the value of R is changed, for example the value of R decrease, then the phase angle becomes larger while the increased value of R will make the phase angle becomes smaller. 3. Based on Figure 7.1, given that the R and C values can be changed, it is possible to make the phase angle: a) 0° and b) 90°? To calculate current in the above circuit, we first need to give a phase angle reference for the voltage source, which is generally assumed to be zero. The total impedance (resistance) of this circuit is the contribution from both the capacitor and resistor. Any resistance and any reactance, separately or in combination (series/parallel), can be and should be represented as single impedance. As with the purely capacitive circuit, the current wave is leading the voltage wave.
    • 11 REFERENCES [1] Rusnani, A. and Mohd, A. M. (2011). Laboratory manual. Electrical Engineering Laboratory 1, EEE 230. [2] Storr, W. (2012). Bipolar transistor basics. Retrieved January 23, 2012, from http://www.electronics-tutorials.ws/transistor/tran_1.html [3] Jones, V. (2001). Basic BJT amplifier configuration. Retrieved January 23, 2012, from http://people.seas.harvard.edu/~jones/es154/lectures/lecture_3/bjt_amps/bjt_a mps.html [4] Alexander, C. K., Sadiku, M. N. O. (2004). Fundamental of electric circuits (2nd Ed.). New York: McGraw Hill. [5] Kalsi, H. S. (2004). Electronic instrumentation (2nd Ed.). New Delhi: Tata McGraw Hill.