Exp 2

INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA REPORTS ON ECE 1101: ENGINEERING LAB - I “EXPERIMENT 2” “KIRCHOFF’S VOLTAGE AND CURRENT LAWS”

No.

Evaluation Items

Marks 20%

1

Introduction

2

2

Objectives

2

3

Equipment list

2

4

Experiment Set-up

2

5

Observations & Data Analysis

6

Conclusion

TOTAL

Marks obtain

10 2

20

Date of Experiment: 10 / 01 / 2011

Date of Submission: 17 / 01 / 2011

SECTION 8

Matric No : 1013467

Name : Mohd Syamsul Bin Ramli.

Matric No : 1017783

Name : Abdul Rahman Bin Baseair.

Matric No : 1011021

Name : Ridzuan Bin Mohamed Seth.

Introduction: Kirchhoff’s Voltage Law (KVL) states that the voltages around a closed path algebraically sum to 0. In other words, the sum of voltage rises equals to the sum of voltage drops. Kirchhoff’s current law (KCL) states that the currents at any node algebraically sum to 0. In other words, the sum of the currents entering a node equals the sum of currents leaving the node.

Objective: •

To verify Kirchoff’s Voltage Law.

•

To verify Kirchoff’s Current Law.

Apparatus: •

One D.C supply 10V.

•

Three digital multimeters.

•

Resistors 300 Ω (2), 330 Ω , 1.8 kΩ , 2.7 kΩ , 3.0 kΩ .

Circuit Diagrams:

Figure 2-1 Method: (a) Kirchoff’s Voltage Law 1. The resistance of each resistors were measured and the measured values were recorded in Table 2-1a. The voltage supply was set at 10V. 2. A similar circuit was constructed as shown in Figure 2-1. 3. The potential difference between each successive pair of lettered terminals for Mesh 1 (A-B, B-C, C-D and D-A) were measured starting from point A. 4. The measured values were recorded in Table 2-1b. 5. The potential difference for the points A-C, C-E and E-A were measured and Kirchoff’s voltage law is verified by using the displayed values. The measured values were recorded in Table 2-1c. (b) Kirchoff’s Current Law 1. The branch currents entering node A were measured by placing ammeter as displayed in Figure 2-1. 2. The magnitude and the direction of the current as indicated by each ammeter were recorded in Table 2-2.

Calculations: Kirchoff Voltage Law(refer to table 2-1b & 2-1c) Measured values: ∑V = VAB + VBC + VCD + VDA = (-0.730 - 7.91 + 9.96 - 1.272) = 0.048 V ∑V = VAC + VCE + VEA = (-8.69 + 9.22 - 0.533) = -0.003 V Theoretical values: ∑V = 0 ∑V = VAB + VBC + VCD + VDA = (-0.739 - 7.964 + 10.00 - 1.297) =0V ∑V = VAC + VCE + VEA = (-8.703 + 9.24478 - 0.54178) =0V %difference VAB = (0.739 – 0.730) / 0.739 x 100 = 1.22% %difference VBC = (7.964 – 7.91) / 7.964 x 100 = 0.68% %difference VCD = (10.00 – 9.96) / 10.00 x 100 = 0.4% %difference VDA = (1.297 – 1.272) / 1.297 x 100 = 1.93% %difference VAC = (8.703 – 8.69) / 8.703 x 100 = 0.15% %difference VCE = (9.24478 – 9.22) / 9.24478 x 100 = 0.27% %difference VEA = (0.54178 – 0.533) / 0.54178 x 100 = 1.62%

Kirchoff’s Current Law(refer to table 2-2) Measured values: ∑I = 0 ∑I = I3 + I4 + I6 = 1.81 + 0.42 - 2.17 = 0.06mA Theoretical values: ∑I = 0 ∑I = I3 + I4 + I6 = 1.806 + 0.432 - 2.238 =0 %difference I3 = (1.806 – 1.81) / 1.806 x 100 = 0.22% %difference I4 = (0.432 – 0.42) / 0.432 x 100 = 2.78% %difference I6 = (2.238 – 2.17) / 2.238 x 100 = 3.04%

Analysis and Deductions: Through this experiment, Kirchhoff’s law has been verified. The test results are almost the same with the simulated PSpice that are provided in the lab manual. But there are some discrepancies due to the value of the resistor that been used in the experiment is not the exact value and there are resistance in other apparatus used that affect the final result. Kirchhoff’s Voltage Law (KVL) states that the voltages around a closed path algebraically sum to 0. In other words, the sum of voltage rises equals to the sum of voltage drops. Kirchhoff’s current law (KCL) states that the currents at any node algebraically sum to 0. In other words, the sum of the currents entering a node equals the sum of currents leaving the node. There are some circuits configurations for which Kirchoff’s Laws are not applicable like in an open circuit configuration because open circuit don’t have a loop nor node. Therefore, open circuit will not be prudent to apply Kirchoff’s Laws.

Discussion: In Experiment 2, our aims are to verify the Kirchhoff’s Voltage Law and Current Law. Firstly, we are required to assemble a circuit according to Figure 2-1 in the manual lab. In the beginning of the experiment, we measured the voltage using the digital multimeter at four points in the circuit, point A-B, point B-C, point C-D and point D-A. The results obtained were recorded in Table 2-1b. From Kirchoff’s Voltage Law, we know that:

VAB + VBC + VCD + VDA = 0

From the results obtained, the percentage differences are merely small. The positive (+) and negative (-) signs in the results show either the voltage drops or rises. Then, we measured the current across three points, R1, R2 and R3. The values obtained were recorded in Table 2-2.According to the Kirchhoff’s Current Law, current across the three points can be calculated using:

R1 + R2 + R3 = 0

Thus, the Kirchhoff’s Current Law was verified. The positive (+) and negative (-) signs in the results show the current’s direction. Since the percentage difference was small, we can say that only few small factors affected the experiment and the results. Firstly, there was resistance in other apparatus used that affected the outcome of the results. The measured value of the resistors that was not equal to the factory values also caused the difference in the results. Conclusion: In this experiment, we have achieved our aim and we can conclude that: Sum of potential difference across a closed circuit is equal to zero. Mathematically: ∑ V = 0;

V1 + V2 + V3 = 0

Sum of current across a closed circuit is equal to zero. Mathematically: ∑ I = 0;

I1 + I2 + I3 = 0

Alhamdulillah, after finished conducting the experiment, we can conclude that the Kirchoff’s current and voltage law are two different laws that are significant to verify a circuit. The summation of voltages around a loop or path is equal to zero and the summation of currents entering is equal to the summation of current leaving the nodes. We also have successfully achieved our objectives since the Kirchoff’s Laws had been verified.