FINAL DATA SHEET
Experiment 5:
Power Measurement and Maximum Power Transfer
Table 5.1 Power Measurements
Internal Resistance (Rin): 466.3
Load Resistance (RL): 469.0
Trial
s
1
Voltage Source
(Vs)
1.038V
Load Voltage
(VL)
0.516V
Load Current
(IL)
1.2 mA
Load Power
(PL)
6.192x10-4 W
2.081V
1.032V
2.4 mA
2.4768x10-3 W
3.030V
1.507V
3.4 mA
5.1238x10-3 W
5.021V
2.503V
5.6 mA
14.0168x10-3 W
7.00V
3.477V
7.6 mA
26.425x10-3 W
9.00V
4.453V
10 mA
44.53x10-3 W
11.09V
5.512V
12.5 mA
68.9x10-3 W
13.03V
6.447V
14.5 mA
93.4815x10-3 W
16.02V
7.95V
18 mA
143.1x10-3 W
10
20V
9.95V
22.5 mA
223.875x10-3 W
Table 5.2 Maximum Power Transfer
Internal Resistance (Rin): 988
Load Voltage
(VL)
1.999V
Load Current
(IL)
14 mA
4.809V
4.850V
Trials
27.99x10-3 W
Load Resistance
(RL)
142.79
11 mA
52.899x10-3 W
437.18
11 mA
53.35x10-3 W
440.9
Load Power (PL)
-3
6.114V
9.5 mA
58.08x10 W
643.58
7.61V
8 mA
60.88x10-3 W
951.25
-3
8.31V
7.5 mA
62.33x10 W
1108
12.52V
2.8 mA
35.06x10-3 W
4471.43
-3
13.79V
1.5 mA
20.69x10 W
9193.33
14.53V
0.8 mA
11.62x10-3 W
18162.5
10
15.03V
0.2 mA
-3
3.006x10 W
SAMPLE COMPUTATION
75150
For Table 5.1
Load Power (PL) = (VL)* (IL)
Trial 1: (0.516V) * (1.2x10-3) = 6.192x10-4 W
Trial 2: (1.032V) * (2.4x10-3) = 2.4768x10-3 W
Trial 3: (1.507V) * (3.4x10-3) = 5.1238x10-3 W
Trial4: (2.503V) * (5.6x10-3) = 14.0168x10-3 W
Trial 5: (3.477V) * (7.6x10-3) = 26.425x10-3 W
Trial 6: (4.453V) * (10x10-3) = 44.53x10-3 W
Trial 7: (5.512V) * (12.5x10-3) = 68.9x10-3 W
Trial 8: (6.447V) * (14.5x10-3) = 93.4815x10-3W
Trial 9: (7.95V) * (18x10-3) = 143.1x10-3W
Trial 10: (9.95V) * (22.5x10-3) = 223.875x10-3W
For Table 5.2
Load Power (PL) = (VL)* (IL)
Load Resistance (RL) = VL / IL
Trial 1:
PL = 1.999V*14 mA = 27.99x10-3 W
RL = 1.999V/14 mA = 142.79
Trial 2:
PL = 4.809V*11 mA = 52.899x10-3 W
RL = 4.809V/11 mA = 437.18
Trial 3:
PL = 4.850V*11 mA = 53.35x10-3 W
RL = 4.850V/11 mA = 440.9
Trial 4:
PL = 6.114V*9.5 mA = 58.08x10-3 W
RL = 6.114V/9.5 mA = 643.58
Trial 5:
PL = 7.61V*8 mA = 60.88x10-3 W
RL = 7.61V/8 mA = 951.25
Trial 6:
PL = 8.31V*7.5 mA = 62.33x10-3 W
RL = 8.31V/7.5 mA = 1108
Trial 7:
PL = 12.52V*2.8 mA = 35.06x10-3 W
RL = 12.52V/2.8 mA = 4471.43
Trial 8:
PL = 13.79V*1.5 mA = 20.69x10-3 W
RL = 13.79V/1.5 mA = 9193.33
Trial 9:
PL = 14.53V*0.8 mA = 11.62x10-3 W
RL = 14.53V/0.8 mA = 18162.5
Trial 10:
PL = 15.03V*0.2 mA = 3.006x10-3 W
RL = 15.03V/0.2 mA = 75150
GRAPHS
Load Voltage vs. Load Resistance
Load Voltage (V)
16
14
12
10
8
6
4
2
0
Load Voltage (VL)
Load resistance (ohms)
Load Current vs. Load Resistance
Load Current (mA)
16
14
12
10
8
6
4
2
0
Load Current
Load Resistance (ohms)
Load Power vs. Load Resistance
0.07
0.06
0.05
0.04
Load Power (Watts)
0.03
Load Power
0.02
0.01
0
Load Resistance (ohms)
DISCUSSION
CONCLUSION
ANSWERS TO QUESTIONS AND PROBLEMS
1.
How much internal resistance does an ideal voltage source have?
2.
How much internal resistance does an ideal current source have?
3.
The internal resistance of an ideal voltage is zero. An ideal voltage
source is a voltage source that supplies constant voltage to a circuit
despite the current which the circuit draws. This means that despite
the resistance which a load may be in a circuit, the source will still
provide constant and steady voltage. When an ideal voltage source has
zero internal resistance, it can drop all of its voltage perfectly across a
load in a circuit. Being that the source has zero internal resistance,
none of the power is wasted due to internal resistance.
The internal resistance of an ideal current source is infinite. The
characteristic of an ideal current or voltage source that makes them
ideal is the fact that neither of them dissipates any power because of
zero internal resistance. Now, since an ideal current source does not
dissipate power in its own internal resistance, the finite parallel resistor
is removed in the equivalent ideal current source circuit leaving an
infinite ohmic value internal resistance in parallel with the ideal current
source.
When is maximum power delivered from a practical source to a load?
When the load impedance equals the source impedance. The
maximum power transfer theorem states that, to obtain maximum
external power from a source with a finite internal resistance, the
resistance of the load must equal the resistance of the source as
viewed from its output terminals.
4.
What are the practical applications of the theory maximum power transfer?
Discuss briefly the different applications.
5.
Determine the maximum power that can be dissipated from the figure below.
6.
When a 4 load is connected to a given generator (practical source) its
terminal/load voltage is 160V. The generators efficiency is 90% when a 9
load is connected to it. Find:
a.
b.
c.
d.
7.
the
the
the
the
maximum power available from the generator.
power transfer efficiency and the power PL, if RL = 50.
power transfer efficiency and the load RL, if PL = 8kW.
load RL and the power PL, if the power transfer efficiency = 65%.
A practical source delivers 5A of current to a load of 5 and it delivers 2A of
current if the load is increased to 20. Find:
a.
b.
c.
d.
the
the
the
the
maximum power available from the source.
power transfer efficiency and the power PL, if the load RL = 10.
power transfer efficiency and the load RL, if PL = 45W.
load RL and the power PL, if the power transfer efficiency = 75%.
REFERENCES
http://www.learningaboutelectronics.com/Articles/Ideal-voltage-source.php
http://en.wikipedia.org/wiki/Voltage_source
http://en.wikipedia.org/wiki/Current_source
http://en.wikipedia.org/wiki/Maximum_power_transfer_theorem
