The George Washington University
School of Engineering and Applied Science
Department of Electrical and Computer Engineering
ECE 2110 - LAB
Experiment # 4
DC Circuits: Ohm's Law, Series and Parallel Circuits
Equipment:
Lab Equipment
(1 Set) Digital Multimeter (DMM)
(2 Pairs) Test Leads
(1 Set) Bread Board
(1 Set) DC Power Supply
Equipment Description
Keithley Model 175 Digital Multimeter (DMM)
Banana to mini-grabber test leads
Prototype Bread Board
Agilent E3631A Triple Output DC Power Supply
Table A – Equipment List
Components:
Kit Part #
Resistor R1
Resistor R2
Resistor R3
Spice Part
Name
R
R
R
Part Description
750Ω Resistor
1.5 KΩ Resistor
3 KΩ Resistor
Table B – Components List
Symbol Name
(used in schematics
throughout this lab manual)
R1
R2
R3
Objectives:









To understand DC series, parallel, and series-parallel combination circuit.
To connect electronic devices on a breadboard.
To calculate DC voltage across resistors in a DC series circuit.
To measure DC voltage across resistors in a DC series circuit using a DMM.
To calculate DC current through resistors in a DC parallel circuit.
To measure DC current through resistors in a DC parallel circuit using a DMM.
To calculate DC current through resistors in a DC series-parallel combination circuit.
To measure DC current through resistors in a DC series-parallel combination circuit using
a DMM.
To calculate the total power dissipated by each resistor in a DC series, parallel, and
series-parallel combination circuit.
GWU SEAS ECE Department ©2012
ECE 2110 – Experiment: DC Circuits: Ohm's Law, Series and Parallel Circuits
Page 1 of 10
Prelab Part 1:
A
●
B
●
C
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Figure 1 – DC Series Circuit
Figure 2 – DC Parallel Circuit
Problem #1 – DC Series Circuit
Figure #1 shows a DC circuit that has two resistors R1 and R2 connected in series with a DC
Voltage Source (The label for the voltage source is VS1).

Circuit Analysis using Ohm's Law
Analyze the circuit in Figure #1. Use VS1=9Vdc. Find the nominal (expected) values for
the DC voltage, DC current and Power Consumption of R1 and R2. Show your steps of
calculations clearly and write down your calculated results in Table 1 (see the lab section
below for table 1).
Problem #2 - DC Parallel Circuit
Figure 2 shows a DC circuit that has two resistors R2 and R3 connected in parallel with a DC
Voltage Source (The label for the voltage source is VS2).

Circuit Analysis using Ohm's Law
Analyze the circuit in Figure #2. Use VS2=9Vdc. Find the nominal (expected) values for
the DC Voltage, DC Current and Power Consumption of R2 and R3. Show your steps of
calculations clearly and write down your calculated results in Table 2 (see the lab section
below for table 2).
GWU SEAS ECE Department ©2012
ECE 2110 – Experiment: DC Circuits: Ohm's Law, Series and Parallel Circuits
Page 2 of 10
Problem #3 – DC Series - Parallel Combination Circuit
Figure 3 – DC Series – Parallel Combination Circuit
Many circuits have a combination of series and parallel resistors. Figure #3 shows a DC circuit
that has two resistors R2 and R3 connected in parallel with one another. R2 and R3 together are
connected in series with resistor R1 and with the DC Voltage Source (The label for the voltage
source is VS3).

Circuit Analysis using Ohm's Law
Analyze the circuit in Figure #3. Use VS3=9Vdc. Find the nominal (expected) values for
the DC Voltage, DC Current and Power Consumption of R1, R2 and R3. Show your
steps of calculations clearly and write down your calculated results in Table 3 (see the lab
section below for table 3).
GWU SEAS ECE Department ©2012
ECE 2110 – Experiment: DC Circuits: Ohm's Law, Series and Parallel Circuits
Page 3 of 10
Prelab Part 2:
During the lab, you will build the three circuits you have analyzed in part 1 of the prelab. You will
then measure the voltage across and the current through each resistor to see if lines up with your
calculated values. In order to make the measurements it is essential that you know how to hook
up the measurement equipment to the circuits you will build.
In this part of the prelab, instructions on how to measure voltage and current are discussed at a
high level. You will be expected to know this and will potentially be quizzed on this knowledge at
the beginning of lab.
A. HOW TO MEAURE VOLTAGE ACROSS A RESISTOR:
A Digital Multimeter (DMM) is a multi-use measurement device we use in the lab to measure
resistance, voltage, and current. You used a DMM in lab 1 to measure the resistance of a
resistor. In this lab you will use the DMM to measure voltage.
Voltage is measured “across” an electrical device. In prelab part 1, figure #1 shows two resistors.
After building the circuit on a breadboard, if we wish to measure the voltage across resistor R1,
we would do the following using the DMM:
1) Set the DMM to measure Voltage by pressing “V” on the DMM front panel
2) Set the meter to the range we expect the voltage to be: (uV, mV, etc.)
3) Attach the two leads/wires coming from the DMM to points A and B in figure #1
a. In this way, the DMM is “ACROSS” R1
4) Read the value of the voltage measured on the DMM
These are the four conceptual steps to measuring voltage. During lab, the exact procedure will
be demonstrated and explained. But it is expected that be familiar with these conceptual steps
prior to the lab. Questions like, “how does one measure the voltage across R2” may appear on a
prelab quiz. If you do not understand these steps, be certain to discuss this with your GTA prior
to lab.
GWU SEAS ECE Department ©2012
ECE 2110 – Experiment: DC Circuits: Ohm's Law, Series and Parallel Circuits
Page 4 of 10
B. HOW TO MEAURE CURRENT THROUGH A RESISTOR:
Current is measured “through” an electrical device and is done very different compared to
measuring voltage. In prelab part 1, figure #1 shows two resistors. After building the circuit on a
breadboard, if we wish to measure the current through resistor R1, we need to BREAK the circuit
where we wish to measure the current. We would do the following using the DMM:
1) Set the DMM to measure Current by pressing “A” on the DMM front panel
(A is for AMPS)
2) Set the meter to the range we expect the current to be: (uA, mA, etc.)
3) Break the circuit where we wish to measure the current
a. In figure #1, we would disconnect/break the circuit at point B
b. Then we can place the two leads/wires of the DMM at the breakpoint as shown in
figure #3
i. The DMM is now in series with the circuit. Because it is series, we know
the current will be the same as it will be through R1 and R2.
c. Now the current will travel from the circuit, THROUGH the DMM, and back to the
circuit
4) Read the value of the current traveling through the DMM
a. This is the value of the current in the series circuit
DMM
(“A” – Mode)
Current
A
●
●
B
●
B
C
●
Figure 4 – DC Series Circuit w/DMM inserted
Prelab Problem #4: Draw the circuit in figure #3. Show how you would attach the DMM to
measure the voltage across R3.
GWU SEAS ECE Department ©2012
ECE 2110 – Experiment: DC Circuits: Ohm's Law, Series and Parallel Circuits
Page 5 of 10
Lab:
Part 1 – DC Series Circuit Measurements
1) Construct the circuit of Figure #1 – DC Series Circuit using your breadboard.
2) Use the Agilent E3631A Triple Output DC Power Supply as VS1 and set the voltage to
9Vdc using the following procedure:
a.
b.
c.
d.
Do not yet connect the Agilent power supply to your circuit!
Press the Power Button to turn it on.
Press Output On/Off once to turn on the output.
Press the +25V button to tell the power supply that we want to alter the output
from the 25V terminals.
e. Use the dial to change the display value to 9 volts. Note: You can safely ignore
the value of the right most digit for this experiment.
f. Once you have reached 9V, Press Output On/Off once to turn the output OFF
while you hook up the circuit.
g. Plug the ‘banana’ end of your cables into the 25V terminals of your power supply.
h. Attaching the mini-grabber ends to your circuit
i. Check whether your circuit configuration is correct or not!
j. If your circuit configuration is correct, press the Output On/Off to apply 9 Volts to
your circuit.
3) Use the DMM (Keithley Model175) to measure the DC voltage across R1 and R2 and
record it in table 1 using the following procedure:
a.
b.
c.
d.
Switch on the Keithley 175 DMM.
Be sure the AC-DC button is unselected (DC is implied by absence of AC label).
Measure DC voltage by pressing the V button.
Select the appropriate voltage range by pressing one of the range buttons or
enable “Auto Range” in order to get the maximum number of significant digits
during measurement
e. Connect the DMM into your circuit. Make sure the DMM is connected in
parallel with the resistor across which you are going to measure the
voltage!
f. Record the voltage (value and corresponding units) from the LCD screen
4) Use the DMM (Keithley Model175) to measure the DC current through R1 and R2 and
record it in table 1.
a. Measure DC current by pressing the A button.
b. Select the appropriate current range by pressing one of the range buttons
c. There is no auto-range for current, you must set it to the range from your
calculations
d. Break your circuit at the point you wish to measure current. Connect the DMM
in series with your circuit as discussed in the prelab.
e. Record the current (value and corresponding units) from the LCD screen
5) Calculate the power consumption of R1 and R2 from the measured DC voltage and DC
current of R1 and R2 and record it in table 1.
GWU SEAS ECE Department ©2012
ECE 2110 – Experiment: DC Circuits: Ohm's Law, Series and Parallel Circuits
Page 6 of 10

Circuit Simulations in PSPICE
Simulate the circuit in Figure 1 using PSPICE (GTA will show you how to configure it in
PSPICE step by step). Find the simulated voltage, current and power consumption of
each resistor using the voltage, current and power probes respectively in PSPICE.
Record your simulated results in Table 1.

Data Analysis
Analyze and interpret Table 1. Include the answers to the following questions when you
are analyzing data:
 What is the total voltage across R1 and R2? Is it equal to the DC source
voltage VS1? If it is (not), why?
 What are the currents flowing through R1 and R2? Are they equal? If they
are (not), why?
Resistors
R1
R2
Electrical Quantities(units)
Voltage (V)
Calculated Nominal
Results
Current (mA)
Power (mW)
Voltage (V)
Measured Results
Current (mA)
Power (mW)
Voltage (V)
Simulated Results
in PSPICE
Current (mA)
Power (mW)
Table 1 – DC Series Circuit Data Table
GWU SEAS ECE Department ©2012
ECE 2110 – Experiment: DC Circuits: Ohm's Law, Series and Parallel Circuits
Page 7 of 10
Part 2 - DC Parallel Circuit Measurements


Construct the circuit of Figure #2 using your breadboard.

Use the Agilent E3631A Triple Output DC Power Supply as VS2 and set the voltage
to 9Vdc. Use the procedure you followed in part 1 to set VS2.

Use the DMM (Keithley Model175) to measure the DC Voltage and DC Current of R2
and R3.

Find the measured Power Consumption of R2 and R3 from the measured DC
Voltage and DC Current of R2 and R3.

Record your measured results in Table 2.
Circuit Simulations in PSPICE
Simulate the circuit in Figure 2 using PSPICE. Find the simulated voltage, current and
power consumption of each resistor using the voltage, current and power probes
respectively in PSPICE. Record your simulated results in Table 2.

Data Analysis
Analyze and interpret Table 2. Include the answers to the following questions when you
are analyzing data:
 What is the total current through the whole circuit? What are the currents
through R2 and R3? What is the relationship between the total current and
the currents flowing through each resistor?
 What are voltages across R2 and R3? Are they equal? If they are (not), why?
Resistors
R2
R3
Electrical Quantities(units)
Voltage (V)
Calculated Nominal
Results
Current (mA)
Power (mW)
Voltage (V)
Measured Results
Current (mA)
Power (mW)
Voltage (V)
Simulated Results
in PSPICE
Current (mA)
Power (mW)
Table 2 – DC Parallel Circuit Data Table
GWU SEAS ECE Department ©2012
ECE 2110 – Experiment: DC Circuits: Ohm's Law, Series and Parallel Circuits
Page 8 of 10
Part 3 – DC Series - Parallel Combination Circuit


Circuit Measurements

Construct the circuit of Figure #3 using your breadboard.

Use the Agilent E3631A Triple Output DC Power Supply as VS3 and set the voltage
to 9Vdc.

Use the DMM (Keithley Model175) to measure the DC Voltage and DC Current of
R1, R2 and R3.

Find the measured Power Consumption of R1, R2 and R3 from the measured DC
Voltage and DC Current of R1, R2 and R3.

Record your measured results in Table 3.
Circuit Simulations in PSPICE
Simulate the circuit in Figure 3 using PSPICE. Find the simulated voltage, current and
power consumption of each resistor using the voltage, current and power probes
respectively in PSPICE. Record your simulated results in Table 3.

Data Analysis
Analyze and interpret Table 3. Include the answers to the following questions when you
are analyzing data:
 What is the current through R1? What are the currents through R2 and R3?
What is the mathematic relationship among the currents through R1, R2 and
R3?
 What are voltages across R1, R2 and R3? What is the mathematic
relationship among the across R1, R2 and R3?
Resistors
R1
R2
R3
Electrical Quantities(units)
Voltage (V)
Calculated
Current (mA)
Nominal Results
Power (mW)
Voltage (V)
Measured
Current (mA)
Results
Power (mW)
Voltage (V)
Simulated
Results in
Current (mA)
PSPICE
Power (mW)
Table 3 – DC Series – Parallel Combination Circuit Data Table
GWU SEAS ECE Department ©2012
ECE 2110 – Experiment: DC Circuits: Ohm's Law, Series and Parallel Circuits
Page 9 of 10
Further Analysis:

Describe the relationship between the total currents flowing through the whole circuit and
the currents through each resistor in Figure 1, 2 and 3, respectively.

Describe the relationship between the source (power supply) voltage and the voltage
drop across each resistor in Figure 1, 2 and 3, respectively.

Compare the nominal results with the measured results and the simulated results of Table
1, Table 2 and Table 3. Explain any differences between the nominal and
measured/simulated results of those Data Tables.
GWU SEAS ECE Department ©2012
ECE 2110 – Experiment: DC Circuits: Ohm's Law, Series and Parallel Circuits
Page 10 of 10