EE-3010
Lab # 2
Simulation of DC Resistive Circuits
Objectives
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Simulate DC Resistive circuits using Electronics Workbench Software.
Verify experimental and theoretically calculated results for a given resistive network.
Investigate potentiometer usage and voltmeter loading effects.
Pre Lab
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Bring a 3.5” diskette to lab. You will need it to save your files.
Read and understand Rizonni Chapter 2.
Do problem 2.30. Determine the current through the 90Ω resistor, current passing through the
8Ω resistor, and the voltage drop across the 22Ω resistor. Bring your detailed solution to lab.
Enter these values on Table 1 of the Data Sheet.
Transfer your measured resistor values from Experiment 1 to Table 2 of the Data Sheet
Transfer your measured voltage and current values from Experiment 1 for voltage source and
resistors to Table 3 of the Data Sheet.
Using your measured resistor values from Experiment 1, calculate theoretical voltages and
currents for the circuit described by Figure 1. Enter these values on Table 3 of the Data Sheet.
Components Used
Electronics Workbench Software for the PC
Part A: Introduction to Electronics Workbench
Procedure
1. The Lab Instructor will demonstrate the construction and simulation of a circuit with Electronics
Workbench software.
2. The Source, Basic, and Indicator parts bins will be used in this experiment to construct a circuit.
The Source parts bin contains the battery (voltage source) and ground components. The Basic
parts bin contains the connector and resistor components. The Indicator parts bin contains the
Voltmeter and Ammeter components. Each of these parts bin can be dragged to form a floating
tool bar.
3. Circuits are constructed in the Circuit Window by dragging components from the Parts Bin
Toolbar. You may rotate components by right clicking the Rotate or flip commands. You may
change the properties of a component by double clicking the component and entering new data in
the dialog box.
4. Components are wired to form a circuit by moving the cursor to the terminal of a component.
Click and drag to connect to another component terminal or circuit path. Connectors may be
utilized to connect multiple circuit paths to a node.
5. Save the completed circuit as a file to your diskette. This circuit can be printed to the network
printer. You may also copy the circuit and paste it in a word document as a circuit schematic and
include with your lab report.
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6. Simulation is performed for the wired circuit by pressing the 1 of the power switch. Voltmeters
will indicate voltage and Ammeters will indicate current.
7. Open the sample circuit provided in lab for Problem 2.30 of the text. Press 1 of the power switch
and record the current value through the 90Ω resistor on Table 1 of the Data Sheet.
8. Add an additional ammeter to the measure the current passing through the 8Ω resistor and a
voltmeter to measure the voltage drop across the 22Ω resistor. Record values for all meters on
Table 1 of the Data Sheet.
Conclusions
1. Does the simulation provide accurate values when compared with calculated values? Explain.
Part B: Parallel and Series Circuit
Procedure:
1. Figure 1 is the schematic for the final circuit constructed in Experiment 1. As a prelab activity,
you should have transferred measured values for R1, R2, R3, and R4 to Table 2 of the Data Sheet.
You should have also transferred measured and calculated values for voltages and currents to
Table 3 of the Data Sheet.
2. Construct a schematic of the circuit shown in Figure 1 using Electronics Workbench. Assign the
measured values from experiment 1 to the components of this schematic. Change the values by
double clicking on the component. Components may be rotated or flipped by right clicking on a
component.
Figure 1
3.
Add Voltmeters and Ammeters to the circuit and measure the voltage drop across each
component and current through each component.
4. Turn the circuit ON and record the values for current and voltage at each component in Table 3 of
the Data Sheet.
Conclusions
1. Does the simulation provide accurate values when compared with both measured values and
calculated values? Explain.
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Part C: Potentiometers and Instrument Loading
A potentiometer is resistance device that has three terminals. It consists of a fixed resistance and a
wiper that can sweep between the range of fixed resistance. Potentiometer applications include
providing an adjustable resistance and as a voltage divider to provide a range of voltages. In Part C
we will be using the potentiometer to construct a voltage divider. We will also investigate meterloading effects for a voltmeter.
Voltmeters have very high resistance that typically exceeds 1 MΩ. If the circuit uses relatively low
resistance components, that is less then 10KΩ, the internal resistance of the voltmeter has a negligible
effect on the circuit. However, this is not always the case. In Part C we will investigate loading
caused by the internal resistance of a voltmeter and its effect on a circuit.
Procedure
1. Construct the circuit shown below using Electronics Workbench. Double click on each meter and
set the internal resistance value of ammeters to 1 mΩ and of the voltmeter to 10 MΩ. Save the
file to diskette.
2. Turn the circuit ON. Verify that the potentiometer value is 50% and record the meter values in
Table 4 of the data sheet.
3. You can slide the slider terminal of the potentiometer by pushing its “Key” letter which is by
default ‘R’. Each time ‘R’ is pressed the potentiometer will increase resistance by 5% of its range.
Each time ‘Shift R’ is pressed the potentiometer will decrease resistance by 5% of its range.
Notice the effect of changing ‘R’ has on the voltages and currents. Comment on this effect in
your lab report.
4. Return the Resistance of the potentiometer to 50% of its range and change the internal resistance
of the Voltmeter to 100 KΩ. Turn the circuit on and record the meter values in Table 4.
5. Return the Resistance of the potentiometer to 50% of its range and change the internal resistance
of the Voltmeter to 1 KΩ. Turn the circuit on and record the meter values in Table 4.
6. Return the Resistance of the potentiometer to 50% of its range and change the internal resistance
of the Voltmeter to 1 MΩ. Also change the resistance of the potentiometer to 1 MΩ by modifying
its value. Turn the circuit on and record the meter values in Table 4 of the data sheet.
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Conclusions
1. What happens when changing the resistance of the potentiometer? Draw a diagram and develop
equations to explain your observations. It may be helpful to use voltage divider equations.
2. Comment on the effect of reducing the internal resistance of the voltmeter. Describe this process
of “loading” using a circuit drawing and develop equations to predict this effect.
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Data Sheet
Table 1: Problem 2.30
Calculated
(Prelab)
Table 3: Parallel and Series Circuit
Simulation
(EWB)
Measured
I90
Vs
I8
Is
V22
V470
Calculated
(Prelab)
Simulation
(EWB)
I470
Table 2: Measured Resistor Values
Nominal Value
(Ohms)
Measured Value
(From Experiment 1)
V1000
I1000
V1500
R1
I1500
R2
V220
R3
I220
R4
Table 4: Potentiometers and Instrument Loading
Item 2
Item 4
Item 5
Item 6
Ammeter 1
Ammeter 2
Voltmeter
Your Name_____________________________
Partner Name___________________________
Lab Instructor___________________________
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Date______________
R.M. Laurie