UNIVERSITY OF NORTH CAROLINA AT CHARLOTTE
Department of Electrical and Computer Engineering
Experiment No. 1 – Orientation and Tutorial
Orientation
Laboratory work is an important part of the ECE undergraduate curriculum. In the lab,
students build circuits and make hands-on measurements to reinforce what is learned in
corresponding lecture courses. Practicing electrical and computer engineers engaged
in product design, development and testing spend significant amounts of time working in
laboratories equipped much like UNC Charlotte’s.
Since most students beginning the laboratory course sequence have never used test
and measurement equipment, it is helpful to spend the first laboratory session exploring
the operation and use of common instrumentation, e.g., the dc power supply,
multimeter, signal generator and oscilloscope. These devices are used throughout the
undergraduate program, and taking the time to learn basic operation at the outset
establishes a solid foundation, while lessening anxiety often associated with performing
the first several experiments.
But first -- a brief overview of ECE laboratory organization, policies, and expectations.
1. Undergraduate ECE students are required to successfully complete four laboratory
courses. Sophomores all take the same two circuits-related courses, while juniors all
take the first electronics lab, and then finish with either the second electronics lab
(Electrical Engineering majors) or digital design lab (Computer Engineering majors).
Table 1 shows the correspondence of laboratory courses to lecture courses, by major.
Laboratory Course
ECGR 2155:
Instrumentation and
Networks
ECGR 2156: Logic and
Networks
ECGR 3155: Systems
and Electronics
ECGR 3156:
Electromagnetic and
Electronic Devices
ECGR 2255: Digital
Design
Lecture Course
ECGR 2111: Network Theory I
Major
EE,
CpE
ECGR 2112: Network Theory II
EE,
CpE
EE,
CpE
ECGR 3131: Fundamentals of
Electronics and
Semiconductors
ECGR 3132: Electronics
ECGR 3181: Logic System
Design II
EE
CpE
Table 1. Undergraduate Laboratory Courses and Corresponding Lecture Classes
2. The primary source for laboratory-related information is the ECE Laboratory Website
http://ece.uncc.edu/component/content/article/13-labs/139-ece-labs.html . All
experimental procedures are accessed via links beneath the course’s header. The
website also contains links to lab policies, equipment manuals, etc. Students are
encouraged to review this material, particularly “10 Rules of Electrical Lab Safety”, “ECE
laboratory Policies”, and the “Code of Student Academic Integrity”.
a. The lab instructor(s) will review the 10 Rules of electrical lab safety during this
lab session, and periodically throughout the program, particularly before
performing experiments involving higher voltages.
b. Laboratory courses are graded as follows:
Report Grade:
Attendance and Participation
Pre-Lab
Quiz
Report (Technical)
Report (English)
Total for each report
Final Course Grade:
Average of All Report Grades
Comprehensive Examination
10 points
10 points
20 points
50 points
10 points
100 points
75%
25%
c. Academic Integrity: Students work together in the laboratory to build circuits and
measure data. Except for discussion and the sharing of data among lab partners,
collaboration ends when the lab session is over. Students must work
independently to write their own pre-lab exercises and reports. There must be no
copying of student-generated text, tables, charts or graphs. Use of text copied
from internet sources, e.g., Wikipedia is strictly forbidden. Raw data aside, any
duplicate work submitted will be viewed as cheating, and will result in disciplinary
action according to university policy. The penalty for a first offense can range
from a formal warning to an F for the course. Regardless of the penalty imposed,
a record of the offense will be kept for eight years in the Office of the Dean of
Students.
3. Lab Kits: Text books are not required for laboratory courses. Instead, students
must provide hand tools, test leads, breadboards, and other items that are used to
set-up and perform experiments. One set of tools is required for each lab working
group - usually two students - and may be shared, although most students prefer to
have their own kits. The same tools are required for all lab courses, so a one-time
purchase covers most student-supplied materials needed for ECGR 2155, 2156,
3155, 3156 and 2255.
STUDENTS WHO HAVE NOT YET ORDERED A LAB KIT, OR ARRANGED TO
SHARE ONE, MUST ORDER A KIT IMMEDIATELY. Ordering information is
provided on the ECE laboratory Website under “Student Supplied Materials.”
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4. Laboratory courses are writing intensive. The graded deliverable for each
laboratory experiment is a formal, written report. Reports are submitted
electronically for grading via the MOODLE site for each laboratory section.
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Pre-Lab Exercise
“Pre-Labs” are prepared and turned in at the beginning of each week’s laboratory
session. They are graded, and account for 20% of the weekly report grade. Pre-labs
are homework assignments that help students to prepare for laboratory experiments.
Here is the Pre-Lab exercise for this experiment.
1. Find and review (do not attempt to read completely) the user manuals for the
following instruments:
•
•
•
•
Agilent E3612A 30W DC Power Supply
Agilent 34401A Digital Multimeter
Tektronix AFG310 Arbitrary Function Generator
Tektronix TDS 2002 Digital Storage Oscilloscope
2. Answer the following questions:
•
•
•
•
•
•
•
•
•
•
For the E3612A power supply, what are the ranges for voltage and current
output?
For the E3612A power supply, what is the procedure for constant current
operation setup?
For the 34401A multimeter, what three basic electrical quantities can be
measured?
What is the maximum dc voltage that can be measured using the 34401A
multimeter?
For the 34401 multimeter, what is the difference in its operation when autozero is
enabled vs. disabled?
What different kinds of waveforms can be generated by the AFG310?
What is the frequency range of the AFG310?
How many signals can be measured simultaneously using the TDS2002?
What is the bandwidth of the TDS2002?
The TDS 2002 displays a Y vs. X graph. What are X and Y?
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Instrumentation Tutorial
The remainder of this laboratory session is devoted to hands-on measurements.
Note: The laboratory instructor will guide students through this first experiment
step-by-step, with students following along. For all other experiments, students
will work on their own in groups, with assistance from the instructor as needed.
1. DC Power Supply
Examine the front panel of the Agilent E3612A power supply (Fig. 1.).
Fig. 1. Agilent E3612A Power Supply
There are three output connectors (+, - and ground), two output control knobs (Voltage
and Current) and an output display.
Turn the power supply on by pressing the power button on the lower left front panel.
Turn the voltage control knob and observe that the display changes to show the dc
voltage appearing between the + and – (red and black) output connectors. Notice that
the current (milliamps) display remains at zero regardless of voltage value. With
nothing connected to the output, no current can flow through the “open circuit”.
Set the voltage to 10 V. Set the (current) range button to 0.5A. Press and hold the CC
Set button while adjusting the Milliamps display to 300 by turning the Current knob.
Release the CC Set button. The current control limit is now set to 0.3A, meaning that
the power supply cannot source more than 300 mA, regardless of what is connected to
the output terminals. This protects equipment from damaging high current due to a
“short circuit” (zero ohms) across the output terminals.
Connect a banana lead (Fig 2.) between the + and – output terminals. The voltage
display becomes zero, and the current display indicates 300 mA, the current limit. No
voltage can appear across a “short circuit”.
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Disconnect the banana lead.
Fig. 2. Banana Lead
2. Digital Multimeter
Examine the front panel of the Agilent 34401A Digital Multimeter (Fig. 3).
Fig. 3. Agilent 34401A Digital Multimeter
The multimeter measures three basic electrical quantities; Voltage (V), Current (I), and
Resistance (Ω). The quantity to be measured is selected by pressing the buttons (DC
V, DC I, AC V, AC I or Ω) directly below the display.
There are five input connections at the right side of the front panel. The column of three
on the far right are most commonly used. The two connections below the label “ Ω 4W
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Sense” are for precision four-wire resistance measurements. This resistance
measurement technique is used in an experiment later in the course.
Returning to the column of three inputs at the far right, notice that the top connector is
labeled “VΩ” and the bottom one is labeled “I”. The “VΩ” terminal is used for measuring
voltage or resistance. The “I” terminal is used for current measurements.
Voltage and resistance are always measured “across” a device (between two points).
Current flows “through” a complete circuit, and must be measured by making the current
flow through the meter. In engineering terminology, a voltmeter is connected in
“parallel”, while an ammeter is connected in “series”.
Press the “Power” button at the lower left of the front panel to turn on the multimeter.
Pres “DC V” to select DC voltage measurement mode. Using two banana leads,
connect the voltmeter in parallel with the power supply output by connecting one
banana lead between the “LO”, or common terminal of the meter and the “-“ output
terminal of the E3612 power supply, and then connecting the other between the “V Ω”
terminal of the meter and the “+” output terminal of the power supply. Compare the
displays of the power supply and multimeter. They indicate essentially the same
voltage, but the multimeter reading is more precise. Disconnect the banana leads from
the power supply + and -.
Locate a resistor mounted on a U channel (Fig. 4.) Use the banana leads to connect
the multimeter to the resistor.
Fig. 4. Resistor
Observe the multimeter display, which reads near zero. The resistance measurement
mode must be selected by pressing the “Ω 4W” button. Do this, and the meter will
indicate the value of the resistor in ohms or kilohms. Record the measured
resistance value, and the value printed on the resistor (nominal) on the DATA
SHEET.
Disconnect all banana leads.
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To measure current, a simple series circuit must be constructed, with the multimeter as
part of the current path. Starting at the “+” output terminal of the E3612 power supply:
• Connect one end of a banana lead to the “+” terminal of the power supply.
Connect the other end to one of the resistor terminals.
• Connect one end of a banana lead to the remaining resistor terminal. Connect
the other end of the banana lead to the “I” input terminal of the multimeter.
• Connect one end of a banana lead to the “LO” input terminal of the multimeter.
Connect the other end to the “-“ output terminal of the power supply.
• Press “Shift” then “DC I” to select DC current measurement mode.
Trace the flow of the current from the positive power supply terminal, through the
resistor and multimeter, and back to the negative power supply terminal. Record the
measured values of current displayed on the multimeter, and voltage displayed
on the power supply, in the DATA SHEET.
Adjust the voltage output of the power supply and observe the change in current. Does
current increase or decrease as voltage increases?
Disconnect the series circuit and turn off the multimeter.
3. Oscilloscope
Examine the front panel of the TDS 2002 Digital Storage Oscilloscope (Fig. 5).
Fig. 5. Tektronix TDS 2002 Digital Storage Oscilloscope
The oscilloscope is most often used to display a graph of voltage vs. time, commonly
known as a “waveform”. The left side of the instrument is the display. Soft keys to the
right of the display select various functions indicated on the display beside them.
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Controls are logically grouped on the right side of the oscilloscope.
Moving from left to right, there are first two columns of controls for the vertical
amplifiers, one set for each of two input channels. This oscilloscope can display two
waveforms simultaneously. The vertical amplifiers control the up-and-down deflection
of the trace(s) on the display.
The next column of controls is for the horizontal amplifier. The horizontal amplifier
controls the speed at which the trace(s) sweep(s) across the display from left to right.
The last column of controls is for triggering. These determine at what point in time the
horizontal sweep begins, based on waveform characteristics.
Turn on the oscilloscope by pressing the power button located on the top of the
instrument. It will take a few minutes for the oscilloscope to self-test and initialize.
Meanwhile, the oscilloscope probe (Fig. 6) can be explained.
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Fig. 6. Oscilloscope Probe
The oscilloscope probe consists of a probe tip and BNC (Bayonet Neill-Concelman)
connector on either end of a coaxial cable. The probe tip – used for connecting to the
circuit where voltage is to be measured -- has a removable, spring-loaded “grabber” that
can be removed (Fig. 7) for probing in restricted areas. The alligator clip is connected
to the “common” or “ground” reference point. (Remember that voltage is always
measured between two points.)
Fig 7. Probe Tip with Grabber Removed
Use the BNC connector at the other end of the coaxial cable to attach the probe to the
oscilloscope’s CH1 or CH2 input. Align the oscilloscope connector’s lugs with the slots
in the probe connector, push, and twist clockwise to lock.
A note of caution when handling the oscilloscope probe: The coaxial cable is relatively
fragile due to its construction, consisting of a fine center conductor surrounded by a
dielectric layer that is covered by a braided shield. The coaxial cable is designed to
provide uniform impedance along its length for efficient signal transfer. Kinking the
cable, rolling over it with a chair, etc. may permanently damage it. Always loosely coil
the probe cable as shown in Fig. 6 before returning it to the lab kit.
DC Voltage Measurement
Press the black “AUTO SET” key at the top right of the oscilloscope’s front panel to
remove any settings made by previous users of the instrument.
To measure DC voltage using the oscilloscope, with the DC power supply on and set to
10V, connect banana leads to the power supply’s “+” and “-“ output connectors.
Connect the oscilloscope probe tip to the positive banana lead, and the ground clip to
the negative lead. See Fig. 8.
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Fig. 8. Probe connections for DC voltage Measurement
In the vertical amplifier section, press the “CH1 MENU” key once or twice, until channel
one menu labels (yellow) appear at the right side of the display beside the soft keys. (If
the blue channel two trace is visible, it can be toggled off by pressing the “CH2 MENU”
button.)
The top soft key selects coupling mode. Press the “coupling” soft key several times to
toggle through the coupling modes “DC”, AC” and “Ground”. In “AC” coupling mode, the
DC component of a signal is filtered out and not displayed. This mode is useful for
measuring small AC components of primarily DC signals, e.g., ripple on the output of a
DC power supply. “DC” (direct coupling) displays the complete signal being measured.
“Ground” short-circuits the channel one input, giving a direct display of the zero volt
reference.
“BW Limit” and Volts/Div soft keys will not be used.
The “Probe” soft key is used to match the oscilloscope input to the multiplication factor
selected by the sliding switch on the probe tip. 1X gives a one-to-one display of the
signal being measured. 10X displays the measured signal at 1/10 of its actual value.
This is used for measuring signals that exceed the oscilloscopes maximum input
voltage specification. For this session, set the oscilloscope and probe to 1X.
Select “DC” coupling and observe the oscilloscope display. Adjust the “position” control
knob of the channel one horizontal amplifier until the yellow “1” arrow at the left of the
display is aligned with the major horizontal axis. This indicates the zero (or ground)
reference voltage. Turn the “VOLTS/DIV” knob above the channel one input until “CH 1
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5.00V” (5V per division) is indicated at the lower left corner of the display. A horizontal
line is displayed two divisions above the reference axis (Fig. 9). The oscilloscope
displays voltage on the vertical axis and sweeps time from left to right along the
horizontal axis. Since the voltage being measured is DC, it does not vary with time and
appears as a flat line. Its magnitude is 2 divisions times 5V per division, or 10 volts.
Fig. 9. Oscilloscope Display of 10V DC Signal
Change the coupling mode from DC to AC. The trace moves to zero volts, because the
measured signal is entirely DC, and this mode removes the DC component. Return to
DC coupling.
The bottom soft key is “Invert”. Press this key once to display the measured voltage as
-10V (2 divisions below the reference.) Note that the measured voltage has not
changed, only the way in which it is displayed.
Toggle “Invert” to “Off”. Turn off the DC power supply and disconnect the banana leads
and oscilloscope probe.
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4. Tektronix AFG 310 Arbitrary Function Generator
Examine the front panel of the Tektronix AFG 310 Arbitrary Function Generator (Fig.
10). Press the power switch in the lower left corner to turn on the instrument.
Fig. 10. AFG 310 Arbitrary Function Generator.
Buttons in the upper right of the front panel select frequency and amplitude input
modes, as well as waveform type. Directly below the display is a keypad used to enter
numerical values for voltage amplitude and frequency. A BNC output connector is
located at the lower right.
Find a coaxial cable having a BNC connector on one end and two alligator clips on the
other (Fig. 11.)
Fig. 11. BNC-to-Alligator Cable
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Attach the BNC end to the function generator output, and connect the other end to the
channel one oscilloscope probe as shown in Fig. 12. Be certain to attach the probe tip
to the red alligator clip.
Fig. 12. Oscilloscope probe connection to BNC-to-Alligator Cable.
To set the function generator to output a 10V, 10 kHz sine wave output:
•
•
•
•
•
•
•
•
Press “FREQ”
Key in “10”
Press “kHz/ms/mV”
Press “ENTER”
Press “AMPL”
Press “10”
Press “Hz/s/V”
Press “ENTER”
The display shows “SINE 10.00000k 10.0”, indicating: 1) sine wave function, 2) 10 kHz,
and 3)10.00 volts. Sine is the default waveform. Other functions, e.g., square, triangle
and ramp waveforms can be selected by using the “FUNC” button and up/down arrows.
Frequency and amplitude can also be changed using the up/down arrows instead of the
keypad.
Observe that the oscilloscope trace indicates zero volts DC. On the function generator,
press the “CH1” button above the output connector. This turns the output on.
Adjust the horizontal amplifier’s “SEC/DIV” knob to obtain a sweep rate of 50µs/div,
which is displayed as 50.0µs at the bottom. The waveform shown in Fig. 13 is
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displayed. Change the sweep rate by turning the “SEC/DIV” knob, and observe the
effect. Return the sweep rate to 50 µs/div.
Turn the channel one “VOLTS/DIV” knob, and observe the effect. Return to 5.00 V/div.
Fig. 13. Oscilloscope Display of 10V 10 kHz Sine Wave
Triggering
Observe that a small yellow arrow appears on the right side of the display. This
indicates the “trigger” level. The oscilloscope trace is produced by repetitive sweeps
across the display at the time rate set with the horizontal amplifier. In order to produce
a stable image, the sweep must start at exactly the same point on the waveform every
time. This is controlled by the trigger.
Press “TRIG MENU” to display the soft key labels. The first soft key shows that the
sweep triggers on the waveform edge. The next soft key, “SOURCE”, is used to select
the channel used to trigger the sweep. The third soft key, SLOPE”, allows the operator
to select triggering on either the rising or falling edge of the input signal. Toggle the
“SLOPE” button several times and notice that the display changes, depending upon
whether the signal is rising or falling through the zero volt, zero time point at the center
of the screen. The “MODE” and “COUPLING” buttons will not be used.
Turn the trigger “Level” knob slowly CW and CCW. Observe that the trace shifts right
and left while the voltage at which the trace crosses the major vertical axis changes.
This trigger voltage is indicated by the arrow at the right of the display, and by the
numerical readout at the lower right corner. Adjust the trigger level to a value higher
than the waveform maximum. The trace jitters due to loss of trigger. Any time a jittery
waveform is encountered, check for proper triggering. Return the trigger level to zero
volts.
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Single-Shot Operation
Continuous triggering can be disabled in order to capture one-time or transient events.
Disconnect the probe tip from the function generator’s red alligator clip. Press the
“SINGLE SEQ” button at the upper right of the oscilloscope. The trigger is now “armed”
and waiting for a signal to initiate a sweep. The triggering legend at the top of the
display has changed from “Auto” to “Ready”. Touch the probe tip to the red alligator
clip. A transient waveform is displayed that clearly shows the point in time (relative to
the trigger point) at which the probe tip contacted the alligator clip. See Fig. 14. This
can be repeated as desired by repeatedly pressing “SINGLE SEQ” to re-arm the trigger.
Fig. 14. Oscilloscope Display of Transient Event
Reconnect the probe tip to the red alligator clip. Return the oscilloscope to continuous
triggering mode by pressing the “RUN/STOP” button.
Persistance
In the persistence mode, an image remains on the display at every point where the
trace has been. This is a carryover from the days of cathode ray tube oscilloscopes
with phosphorescent displays.
Be sure that the 10V 10 kHz sine wave is displayed as shown in Fig. 13. Press
“DISPLAY” above the channel two vertical amplifier controls. Toggle the “Persist” soft
key to “Infinite”. Turn the trigger level knob to move the trace left and right on the
display, observing the effect of the persistence mode.
Use the “Persist” soft key to toggle persistence “Off”. Return the trigger level to zero
volts.
Cursors
Press the “CURSOR” button above the vertical amplifier controls. Toggle “Type” to
“Voltage”. Parallel horizontal lines appear on the display. Green LED’s beside the
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vertical amplifier “POSITION” controls indicate that these knobs now control “CURSOR
1” and “CURSOR 2”. Turn these knobs to position the voltage cursors on the positive
and negative peaks of the sine wave. To the right of the display, individual voltage
values for the two cursors appear, along with the “Delta” or difference in voltage
between them. The peak-to-peak voltage of the sine wave is 20 V.
Toggle the “Type” soft key again to display vertical cursors for measuring time and time
differences. Notice that the oscilloscope also calculates and displays waveform
frequency in the lower right corner.
Press the “Type” soft key once more to turn off cursors.
Two Channel Operation
Connect another probe’s BNC end to the oscilloscope’s channel two input. Connect its
probe end in parallel with the channel one probe, across the function generator output
as shown in Fig. 15.
Fig. 15. Two Channel Oscilloscope Probe Connections
Press the “CH 2 MENU” button to activate the channel two trace. Adjust the channel
two “VOLTS/DIV” knob to 5.00 V/div. The blue trace of channel two now overlays the
yellow trace of channel one. Separate the two traces by turning the “POSITION” knobs
for each channel (Fig. 16). Return the traces to their overlaid positions at the center of
the display.
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Fig. 16. Two Oscilloscope Traces Separated by Using the “Position” Controls
Two traces can also be separated by using the “Invert” function. Press “CH 2 MENU” to
activate the channel two soft keys. Invert the channel two signal by pressing the “Invert”
soft key. Fig. 17 shows the display for two identical signals with channel two inverted.
Fig. 17. Two Oscilloscope Traces Separated by Inverting the Channel Two Signal
X-Y Mode Operation
All oscilloscope traces so far have been displayed in Y-T mode, i.e., voltage on the
vertical (Y) axis vs. time on the horizontal axis. It is sometimes advantageous to
eliminate time as the independent variable and display one voltage as a function of the
other. In the X-Y mode, channel two voltage is plotted against channel one voltage,
where channel one is the horizontal (X) axis and channel two is the vertical (Y) axis.
Press “DISPLAY”, and then toggle the “Format” soft key to “XY”. The trace changes to
a straight line with slope of minus one. The channel two signal increases as the
channel one signal decreases, and at the same rate, and vice-versa. See Fig. 18.
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Fig. 18. Two Oscilloscope Traces Displayed in X-Y Mode
The X-Y mode is most often used for displaying current vs. voltage, or for creating
Lissajous patterns that graphically show the phase difference between two signals. In
this example, the phase difference is 180°. For phase differences other than 0° or 180°,
which are special cases, the Lissajous pattern is an oval of varying width. Intricate
Lissajous patterns result when comparing signals of different frequencies.
Summary
This concludes the introduction to essential laboratory instruments. Students will use
these instruments and the operational knowledge gained through this experiment for all
four undergraduate laboratory courses, course projects, Junior and Senior Design
classes, and possibly throughout their careers.
The instruments cannot be permanently damaged by settings made using the front
panel controls. As with learning new software, the best way to gain familiarity and
expertise with the equipment is to exercise it hands-on. The laboratory is yours to use
for learning. Never be reluctant to hook up the instruments and use them.
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DATA SHEET
Nominal Resistance _____________________
Measured Resistance ____________________
Measured Voltage across the Resistor _______________
Measured Current through the Resistor _______________
INSTRUCTOR'S INITIALS:
DATE:
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POST-LAB QUESTIONS
Post-Lab questions must be answered in each experiment’s laboratory report.
1. Apply Ohm’s law, V=IR, to explain why no voltage can appear across a short
circuit.
2. How does Ohm’s law explain observed current change with increasing voltage
across the resistor?
3. Use the voltage and current values recorded for the resistor to calculate the
resistor’s value. Compare this calculated value to the resistance measured with
the multimeter, and the value printed on the resistor.
4. Describe the oscilloscope trace that would result from displaying two identical
signals (no inversion) in X-Y mode.
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