Lab 12: Superposition Theorem (Open Ended) OBJECTIVES: Implementation of super position method. Comparison of the measured, calculated and simulated values. APPARATUS: Variable Resistance, Resistor, Digital Multi Meter (DMM), Breadboard, Power Supply, Connecting wires etc Inlab Figure 1 ( Circuit For 10V ) Figure 2 ( Circuit For 5V ) 1 Figure 3 (complete circuit) OBSERVATIONS AND CALCULATIONS: Voltage/Current R2=10 ohms R4=100 kilo ohms Calculated Measured Simulated Calculated Measured Simulated V1 4.29 4.35 5 10 10.1 10 V2 2.14 2.13 2.5 5 4.9 5 V3 6.43 6.48 7.5 15 15 15 I1 0.42 0.43 0.42 0.1 0.1 0.2 I2 0.21 0.21 0.23 0.05 0.04 0.05 I3 0.63 0.64 0.65 0.05 0.05 0.05 Table 1 (Calculated, Measured and Simulated Values) 2 Post Lab Questions? 1. The Superposition Theorem works nicely to calculate voltages and currents in resistor circuits. But can it be used to calculate power dissipations as well? Why or why not? ANS: Superposition theorem can be applied in linear circuits to find out the voltage or current. Using the net value of voltage, after considering all the sources you can use it to calculate the power. However, if you try to calculate the power for each source separately and then add them, there may rise condition where you'll get a wrong result. An example will make this clearer. Current due to source 1: I1 Current due to source 2: I2 Now if you directly consider power, you'll get (I12+I22) R(I12+I22) R But the actual power is (I1+I2)2R(I1+I2)2R for currents flowing in same direction for the two sources (I1−I2)2R(I1−I2)2R for currents flowing in opposite direction for the two sources 2. What advantages and disadvantages are associated with Superposition Theorem? ANS: Advantages - It is applicable to the elements of the network as well as to the sources. It is very useful for circuit analysis. It is utilized to convert any circuit into its Thevenin equivalent or Norton equivalent. Disadvantages - Superposition is applicable to current and voltage but not to power. It cannot be used for unbalanced bridge circuits. 3 3. How are dependent voltage and current sources dealt with when using Superposition Theorem? ANS: In superposition theorem we replace voltage source and current source by short circuit and open circuit respectively. This is because they are replaced with their equivalent impedances. 4. What is power rating of resistor? A resistor sometimes becomes hot while connected in the circuit. What can be the reason for this? ANS: When an electrical current passes through a resistor due to the presence of a voltage across it, electrical energy is lost by the resistor in the form of heat and the greater this current flow the hotter the resistor will get. This is known as the Resistor Power Rating. Conclusion: The Super position theorem states that in any linear network containing two or more sources, the response in any element is equal to the sum of the responses caused by individual sources acting alone while the other sources are made inoperative. As a conclusion, it is can be said that the objective of the experiment which is to verify experimentally the Superposition Theorem was achieved successfully. The discrepancies were small; thus the results can be accepted. 4