Name
Date
(Lab Partner)
Lab 6: Direct Current Circuits
Introduction
Insert your introduction here. Write a few lines describing the goals of the lab and basic
principles. Include any important equations that you will use.
Part I: Investigation of Voltage, Resistance, and Current
Table 1
Insert data table here. You can get a template for the table from the course website.
Graph 1
Insert graph 1 (V vs. I) and 2 (C vs. A) here. Be sure that each graph has a label, that the
axes are labeled (including units), and display the equation of the trendline on the graph.
Also include results from regression.
Analysis Part I
3. What is the value of the slope? Compare it to the resistor value. Do they agree?
Note that resistors are manufactured such that their actual value is within a tolerance.
For most resistors used in this lab, the tolerance is 5% or 10%. Check with your
instructor to determine the tolerance of the resistors you are using. Calculate the range
of values for each resistor. Does the constant in each equation fit within the
appropriate range of values for each resistor?
4. Do the resistors obey Ohm’s law? That is, do they all give you a straight line? If not,
propose an explanation.
5. Describe what happened to the current through the light bulb as the potential
difference increased. Was the change linear? Since a change in the slope of the linear
regression line is a measure of a change in resistance, describe what happened to the
resistance as the voltage increased. Since the bulb gets brighter as it gets hotter, how
does the resistance vary with temperature?
6. Does your light bulb follow Ohm’s law? Base your answer on your experimental
data.
Part II: Investigation of Series and Parallel Circuits
Preliminary Question
Insert Table 2 here. You can get a template for the table from the course website.
Tables 3 and 4
Insert data table here. You can get a template for the table from the course website.
Analysis Part II
Section II-A: Series Circuits
1. What is the relationship between the three voltage readings: V1, V2, and VTOT?
2. Using the measurements you made for I and VTOT and your knowledge of Ohm’s law
(V=IR), calculate the equivalent resistance (Req) of the circuit for the two series
circuits you tested.
3. Study the equivalent resistance readings for the series circuits. Can you come up with
a rule for the equivalent resistance (Req) of a series circuit with two resistors?
1. For each of the series circuits, compare the experimental results with the resistance
calculated using your rule. In evaluating your results, consider the tolerance of each
resistor by using the minimum and maximum values in your calculations.
2. Examine the currents you measured for the series circuits. What is the relationship
between the total current and the currents through each of the resistors?
Section II-B: Parallel Circuits
1. Using the measurements you made for I and VTOT and your knowledge of Ohm’s law,
calculate the equivalent resistance (Req) of the circuit for the two parallel circuits you
tested.
2. Study the equivalent resistance readings for the parallel circuits. Devise a rule for the
equivalent resistance of a parallel circuit of two resistors.
3. What do you notice about the relationship between the three voltage readings V1, V2,
and VTOT in parallel circuits?
4. Examine the currents you measured for the parallel circuits. What is the relationship
between the total current and the currents through each of the resistors?
5. If the two measured currents in your parallel circuit were not the same, which resistor
had the larger current going through it? Why?
6. Compare the total currents through the parallel circuits to the total current flowing
through the series circuits. Which has the largest total current? Why?
Conclusion
Write a few concluding remarks.
Sample Calculations
Insert any sample calculations here. These may be added by hand.