Capitol College
Spring Semester 2000
Lab Experiment #2
Andy Buettner
Instructor: Dr. Thomas
Due: February 18^{th}, 2000
Received: ___________________
Objectives
The Objectives of this lab were to study the relationships that exist within series  parallel circuits, and to be able to calculate and measure current through specific points. Additionally, use that knowledge to indirectly calculate the internal resistance of a power source.
Equipment Used
Equipment used
ET  3100 Trainer ser no: 1614
Fluke DMM ser no: 31101515
Components used
1) EE  159 lab kit
Procedures
Assemble Circuit and record individual resistances
Power the circuit to 5 volts
Measure the voltage across each resistor
Calculate currents through each resistor
Measure the current through the whole circuit
Part 2: Parallel Circuits
Assemble the circuit and measure the resistance of each resistor, and the total resistance of the circuit
Power the circuit to 5 volts and record the currents through each resistor
Calculate the current through each resistor
Part 3: Internal Resistance
Set the trainer to exactly 1.5v
Connect a 100ohm resistor between the positive and negative terminals.
Measure the voltage, and calculate the internal voltage drop and resistance.
Schematic Diagram for part III
Results
Table #1: Part 1 master

Resistor 1 
Resistor 2 
Resistor 3 
Measured Resistance 
151.6W 
329.5W 
459.0W 
Measured Voltage 
.804V 
1.754V 
2.443V 
Calculated Current 
5.303ma 
5.323ma 
5.322ma 
Measured Current 
5.27ma 
5.27ma 
5.27ma 
Table #2: Part 2 master

Resistor #1 
Resistor #2 
Resistor #3 
Measured Resistance 
1.195KW 
2.197KW 
3.248KW 
Measured Voltage 
5.00V 
5.00V 
5.00V 
Calculated Current 
4.184ma 
2.295ma 
1.539ma 
Measured Current 
3.846ma 
2.187ma 
1.488ma 
Answers to Questions
Q: Compare the calculated currents with the obtained in Table 1: Is the difference expected and why?
A: Yes, the internal resistance of the DMM caused the difference.
Q: Do the same for table 2.
A: Yes, the internal resistance caused a voltage drop across the circuit thus causing a decrease in current.
Q: What was the internal resistance of the Trainer?
A: 3.988W
Q: What is the percent voltage regulation of the Trainer?
A: 0.40%
Q: Is R_{total }equivalent to what is expected?
A: Yes.
Q: Is the total voltage drop in part 1 equal to 5 volts?
A: The total calculated voltage drop is 5.001V; therefore, yes.
Q: Was the R_{total} what was expected?
A: Yes.
Q: Does each current added up equal I_{total}?
A: I_{total} = 8.018ma: Yes, they are equal.
V_{2} = 4 volts
V_{2} = 4.0 volts
V_{2} = 3.87 volts: The meter creating a significant difference in the total resistance causes the difference.
V_{2} = 3 volts
Conclusions
My experiences have shown that current is easier and more accurate to derive than any other value in the Ohm's law equation. Additionally, making current measurements adds the most error to results than measuring any other value. Also, calculating the internal resistance of the Trainer had a lot of error in it as the only digit that would have value would be the last digit, which had little significance. A different source, or a better way of determining the voltage drop would be needed.
Attachments
Original handouts
Original data
Calculations