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University of Technology Laser and Optoelectronics Engineering Department Direct Current Circuits Analysis Laboratory 2011-2012 Experiment No.( 13 ) Maximum Power Transfer Theorem Aim of experiment: To prove Maximum Power Transfer theorem practically. Apparatus 1. DC circuit training system 2. Set of wires. 3. DC Power supply 4. Digital A.V.O. meter Theory The power transferred from a supply source to a load is at its maximum when the resistance of the load is equal to the internal resistance of the source. On the other words" A resistive load will be consumptive maximum power from the supply when the load resister is equal to the equivalent (Thevenin) network resister" RL = Rth ……. For maximum power transfer. IL = Vth / (Rth + RL) = Vth / (Rth + Rth) = Vth / 2 Rth Where, Pmax = IL2 RL = Vth2 / 4Rth A graph of RL against P is shown in Fig.(1), the maximum value of power which occurs when RL = Rth. 1 University of Technology Laser and Optoelectronics Engineering Department Direct Current Circuits Analysis Laboratory 2011-2012 Fig.(1) Procedure 1. Connect the circuit shown in figure below. From the circuit, we can note that Rth=100 and Vth=5V. 2. Change the value of RL in steps as shown in table. 3. Measure the voltage "VL" and current "IL" and record it in the table. 4. Repeat steps (2-3) by using Rth = 150 R(Ω) 20 40 60 80 100 IL(mA) VL(volt) Power 2 120 150 180 220 300 University of Technology Laser and Optoelectronics Engineering Department Direct Current Circuits Analysis Laboratory 2011-2012 100 Rth VL V 500 Vth IL A 5V RL Discussion and calculation: 1. Plot the curve of the power against the load resistance and determine the maximum power. 2. Compare between the theoretical and practical results. 3. Comment on your results. 4. Find RL for the maximum power transfer in the circuit shown. RL 3 University of Technology Laser and Optoelectronics Engineering Department Direct Current Circuits Analysis Laboratory 2011-2012 4