Lab 7: Maximum Power Transfer

Introduction:
In the real world, the efficiency of any machine is one of the most important things that engineers need to consider when design it. When we want to have best efficiency, we want to have the maximum power output. Therefore, the Maximum Power Transfer Theorem helps us have an ideal how to maximize the power transfer from a circuit to a resistive load. In this experiment, we will verify the Maximum Power Transfer Theorem in a simple circuit, and use it to determine the Thevinin Resistance.

Procedure:

Part A:
Build the simple circuit as shown below:

 

Measured Value of 5.6 KΩ resistor	Measured value of 4.5V source
5.54 +/- 0.01 KΩ	4.66 +/- 0.01 V

 Measurement:

Measured V0 (V)	Measured R0 (KΩ)	Calculated P (mW)
0.00	0	0.000
0.39	0.51	0.298
0.70	1.02	0.480
0.92	1.43	0.592
1.10	1.82	0.665
1.30	2.34	0.722
1.49	2.89	0.768
1.60	3.27	0.783
1.79	3.99	0.803
1.92	4.54	0.812
2.00	4.93	0.811
2.09	5.45	0.801
2.20	6.07	0.797
2.30	6.78	0.780
2.40	7.54	0.764
2.51	8.54	0.738
2.55	8.94	0.727

 

  From the measurements, we can see that R_o = 4.54 KΩ results in a maximum power transfer which is 0.812 mW.

The maximum power from the circuit occurs when Ro = Rth = 5.54 KΩ .
 % error = (4.54 - 5.54)/5.54 = 17.3 %.


Part B:

Build the circuit as shown below:

Data:

Measured R1	Measured R2	Measured R3	Measured R4	Measured R5
0.975 KΩ	9.87 KΩ	9.88 KΩ	0.975  KΩ	0.978 KΩ

Measured Value of 4.5V source	Measured Value of 9.0 V source
4.53 V	9.10 V

Theoretical:

The graphs of current, voltage and power through potentiometer  versus resistance.

Using Schematics, the application on Pspice, we can theoretical graph the power through Potentiometer:

Conclusion:
Based on the 2 methods we used to measured the maximum power transfer to the Load. The method in which we using the multimeter to measure the resistance and voltage across the Load is more accurate. The method using LabPro, current and voltage sensors to measure voltage and current is not accurate because the current sensor is unregulated about 0.2mA. However, the current through the Load is in order that the current sensor is unregulated, so we cannot measure the current accurate.