Download Name:

Name:
Lab Partner(s):
Date lab performed:
Dr. Julie J. Nazareth
Physics 123L/133L
Section:
Response of Circuit Elements
Part 1: Resistance and Current Measurements for a Carbon Resistor
Color Code Colors (left to right):
Color Code Numerical Resistance ( Ohms)
Color Code tolerance (%)
Color Code tolerance ( Ohms)
Ohmmeter Resistance, Rm ( Ohms):
Voltage, V (volts)
Current, I ( A)
Voltage, V (volts)
Current, I (
5.0
-0.5
4.0
-1.0
3.0
-2.0
2.0
-3.0
1.0
-4.0
0.5
-5.0
Part 2: Resistance and Current Measurements for a Light Bulb
Ohmmeter Resistance, RM ( Ohms)
Voltage, V (volts)
Current, I ( A)
Voltage, V (volts)
Current, I (
5.0
0.8
4.0
0.7
3.0
0.6
2.0
0.5
1.5
0.4
1.3
0.3
1.1
0.2
1.0
0.1
0.9
0.05
A)
A)
Part 3: Voltage and Current Measurements for a given Power Supply Voltage for a Diode
Ohmmeter resistance, RM ( Ohms): Forward =
Reverse =
Forward Bias
Reverse Bias (reverse leads not diode)
Power Supply
Power Supply
Voltage,
Voltage,
Current,
Voltage,
Voltage,
Current,
VS (volts)
V (volts)
I ( A)
VS (volts)
V (volts)
I ( A)
40
-40
30
-30
20
-20
10
-10
5
-5
3
-3
2
-2
1
-1
Lab: Circuit Elements
Updated 01/23/2013
Data & Reporting score:
Graphs and Calculations: Plot the following graphs on separate sheets of paper. Use most of the
sheet of paper to draw your graph and remember to title and label your graph properly. When
calculating the local slope, draw your line tangent to the curve at the point instructed. Put the
calculation of the local slope on your graph, in an unused section of the paper. Draw a small box
or circle around the points (not data points!) you used to calculate the slope. Don’t forget to title
and label your graphs appropriately. If graphs are completed (and required slopes
calculated) before leaving class, each group only needs to complete one set (the instructor
must sign off). All lab partners in the group will receive the same score for the graph and
slope calculation potion of the grade, if sharing graphs. If the graphs are not completed
(and required slopes calculated) before leaving class, then each lab partner must complete
their own graphs to turn in with their lab report.
Graph 1: Plot the voltage versus current (V vs. I) for a Carbon Resistor. Draw a best fit line to
your data points and calculate the slope of the line (dynamic resistance).
Using Graph 1 (Part 1, Carbon Resistor) show the following calculations with units:
- static resistance at 3.0 volts, RS = V/I
- dynamic resistance, RD = slope of best fit line
(put this calculation on graph in an unused section of the paper)
Carbon Resistor Resistance Results: Comparing Measurements
Ohmmeter
Code Resistance,
Resistance,
Static Resistance Dynamic Resistance
RC ( Ohms)
RM ( Ohms)
RS ( Ohms)
RD ( Ohms)
Graph 2: Plot the voltage versus current (V vs. I) for a Light Bulb. Sketch a best fit curve to
your data. Choose a “cold” point (near 0.2-0.5 volts) and a “hot” point (near 4-5 volts) on
the curve, mark the points with an “X”, and label them. Draw tangent lines for the “cold”
and “hot” dynamic resistances. Use two easy to read points on the tangent lines to calculate
the local slopes.
Using Graph 2 (Part 2, Light Bulb) show the following calculations with units:
- “cold” static resistance, RCS = VC/IC
- “hot” static resistance, RHS = VH/IH
- “cold” dynamic resistance, RCD = local slope = slope of tangent line
(put this calculation on graph in an unused section of the paper)
- “hot” dynamic resistance, RHD = local slope = slope of tangent line
(put this calculation on graph in an unused section of the paper)
Lab: Response of Circuit Elements
Updated 01/23/2013
Light Bulb Resistance Results: Comparing Measurements
“Cold” Point
“Hot” Point
Ohmmeter,
Static
Dynamic
Static
Dynamic
RM ( Ohms)
( Ohms)
( Ohms)
( Ohms)
( Ohms)
Graph 3: Plot the measured voltage versus current (V vs. I) for a Diode. (Do not use the power
supply voltage in your graph.) Sketch a best fit curve to your data. You might get a plot
something like the curve shown below. Determine the dynamic resistance near -2 volts in
the reverse bias direction and near 1 mA in the forward bias direction. Also, label the areas
#1, #2, and #3 on your graph 3 as either “High R” (high resistance) or “Low R” (low
resistance). See the sketch below to see which areas on your graph 3 are #1, #2, and #3.
V
Area #1: High resistance or low resistance? (Mark on your
graph)
#1
#2
#3
I
Area #2: High resistance or low resistance? (Mark on your
graph)
Area #3: High resistance or low resistance? (Mark on your
graph)
Using Graph 3 (Part 3, Diode) show the following calculations with units:
- dynamic resistance near -2 volts in the reverse bias direction, RRB
(put this calculation on graph in an unused section of the paper)
- dynamic resistance near 1 mA in the forward bias direction, RFB
(put this calculation on graph in an unused section of the paper)
Diode Dynamic Resistance Results: Comparing Measurements
Reverse Bias Dynamic Resistance,
Forward Bias Dynamic Resistance,
RRB ( Ohms)
RFB ( Ohms)
Don’t forget to write your summary! (As always, start with an introductory sentence that tells
the reader the purpose/objective of this particular lab. Some things to consider before writing
your summary/conclusion paragraph: How do the static and dynamic resistance of the carbon
resistor compare with each other? How do those values compare with the ohmmeter reading …
and the color code? Be specific and if there are differences between the values, discuss why that
might be so. How do the various resistance measurements for the light bulb compare? With
which resistance measurement from graph 2 does the ohmmeter measurement, RM, most nearly
agree? Why do you think that is? What does the shape of the diode curve (graph 3) tell you
about the resistance of and flow of current through a diode? What was happening to the current
flow at #2 on your graph 3?)
Lab: Response of Circuit Elements
Updated 01/23/2013