Module 6: RC Circuits
This week you will charge and discharge a capacitor in an RC circuit and take advantage of the sample rate of the IOLab. Since the voltage across the capacitor changes during the charging and discharging process, we can use a 100Hz sample rate to observe this change with measurements taken 100 times a second. Then, we can examine how the rate of the change in the measured voltage can be described by exponential functions with parameters determined by the effective capacitance and resistance of the circuit.
Objectives
In this lab, you will:
- Build a complete circuit matching the arrangements of circuit elements (wires, capacitors, resistors, and power supply) according to a circuit diagram,
- Charge and discharge a capacitor, measuring the voltage across the capacitor as a function of time with the IOLab.
- Perform a trendline analysis after linearizing the voltage data to determine how the estimates for the linear regression analysis correspond to the resistance and capacitance of the circuit.
- Perform a half-life analysis to estimate the time constant for the circuit.
- Make quantitative predictions for how changes in the capacitance or resistance of the circuit affect the time constant.
Read the Lab Document Download Lab Document
The lab document contains theoretical background for analyzing RC circuits, which supplements what you've read about in the lecture course. Read through the introduction, theory, and experimental procedure before opening the lesson file to get an overview of the aims of this experiment.
Download the IOLab Lesson File
Almost all of your experimental data collection and analysis will occur in this lesson file, which will be downloaded and imported into the IOLab application. After completing the slides, you will export and upload this completed lesson file to Canvas to serve as your lab report for evaluation.
There is limited analysis in Excel to complete. There is no template for presenting this analysis. Instead you will upload an Excel file containing two plots (VS vs. t, and ln(VS) vs. t) along with three columns of data (t, Vs, and ln(VS)).
This download
Download This download
provides a zip file containing a folder that needs to be moved to a specific location on your computer. First, open the zip file. Then move the Lab6-RCCircuits folder to your "activities" folder located on your machine in the following location (OS X or Windows): "../Documents/IOLab-WorkFiles/activities". If you do not see an "activities" folder inside the IOLab-Workfiles folder, then create a new folder in this location and name it "activities."
Watch this video of a screen recording following these directions. (02:59)
Lab Set Up and Data Collection
Lab Materials and Setup Videos -
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Lab Materials
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Setup Videos |
Using IOLab Lesson Player
After you download the lesson and place it in the correct folder on your computer, follow these directions to access the first IOLab Lesson:
- Open the IO Lab Program.
- Click the folder icon on the toolbar.
- Select "Lesson List" to reveal the available lessons.
- Choose Lab6-RCCircuits which opens the lesson to the first slide.
- Complete the directions on each slide and click Save & Next Slide to move through the lesson.
- View the important tips below to inform you of some quirks with the lesson player. It may affect how you work through this lab.
- Lab reports are automatically generated as you work through each lesson. Instructions for accessing these reports are below as well.
Important Tips for Operating the Lesson Player
Once you are in the Lesson Player, keep in mind the following tips:
- Make sure your IOLab cart is connected and maintains communication with the computer. Any issues with losing a connection during a collection of data may cause the lesson player to crash or lose some functionality.
- As the batteries weaken, the cart may shut off for no apparent reason. If this happens, replace the batteries using the multitool provided in the lab supplies and begin a new lab report (hit Restart button).
- If your lesson crashes, restart the lesson from the beginning slide. Do not try to access any previously stored lesson data from the crashed session.
- It may help to delete data stored from lessons where the player crashed. Delete data reports by clicking the trash can beside the report you want to remove. This is done at the same place where you can rename or export saved lab reports (see below).
- You can always return to previously completed slides in the lesson player, but be forewarned to not change any of the data acquisitions on slides that were already saved. Once you save a slide, you should consider the data on that slide as frozen (since later slides may use this data). The only way to delete information on a saved slide is to click the "RESTART" button on the player -- which begins a new lab report from scratch.
- NOTE: you can return to a previously saved slide to change a response to a question (unless it is a prediction question, which the edit feature is disabled for obvious reasons).
Accessing your Saved Lab Report
As you complete each slide in the lesson, a report is generated with this saved data. When you are finished with the lesson, edit the report with your name and a few comments by following these directions:
- Click the folder icon on the toolbar.
- Select "Lesson List" to reveal the available lessons.
- Find the Lab6-RCCircuits lesson.
- Click the "Show Reports (X)" link. "X" will equal the number of times you have used this specific lesson.
- Each report has a time stamp that will help identify the report you would like to rename and use when submitting to Canvas.
- Click on the pencil icon for the report you want to edit. Add your name and any comments. Then click Save.
Exporting your Saved Lab Report for Submission
Finally, prepare the lab report for submission by exporting the report to a few comments by following these directions:
- Find the report you want to submit in the list of lessons (see above).
- Click on the icon to the left of the pencil to save your lesson to your computer. Put it somewhere you can find it, since you will need to select it later to upload to Canvas.
- Go to the destination folder on your computer and make sure it appears where you think you placed it.
- Submit this file like you would any other file submission in Canvas.
Discussion Posting
Use this discussion board as a forum to compare results and make sense of the analysis completed during this week's lab.
Upload and submit the artifacts from this week's lab by Sunday at 11:59PM EST.
Upload the Lesson file to the assignment Lab 6 - RC Circuits Lesson File Upload
Upload the Excel file to the assignment Lab 6 - RC Circuits Excel Spreadsheet Upload