Education Technology

# Activities

• ##### Subject Area

• Math: Algebra I: Exponential Functions
• Math: Algebra II: Logarithms and Exponentials

9-12

60 Minutes

• ##### Device
• TI-73 Explorer™
• TI-83 Plus Family
• TI-84 Plus
• TI-84 Plus Silver Edition

TI Connect™

• ##### Accessories

CBL™/CBL 2™
Sensor - Voltage
TI Connectivity Cable
Vernier LabPro®

• ##### Other Materials
This is Activity 18 from the EXPLORATIONS Book:
Real-World Math Made Easy.

The following materials are required for this activity:
• 9-volt battery
• 100 k-ohm resistor
• 220 microfarad capacitor

## Charging Up, Charging Down: Exponential Models

#### Activity Overview

In this activity, students' will use a voltage probe to collect voltage data from a discharging capacitor. They will model potential data using an exponential function.

#### Before the Activity

• Connect the voltage probe to Channel 1 on the CBL 2™ or Vernier LabPro®
• Connect the CBL 2 or LabPro to the calculator using the Unit-to-Unit cable
• See the attached PDF file for detailed instructions for this activity
• Print pages 175 - 182 from the attached PDF file for your class
• #### During the Activity

Distribute the pages to your class.

Follow the Activity procedures:

• Connect the voltage probe and resistor across the capacitor
• Verify that the wires are in the correct position to confirm that the capacitor is charged
• After the capacitor is charged, remove the battery from the circuit and begin data collection
• Examine the graph of potential versus time displayed on the calculator and record the y-intercept on the Data Sheet
• Graph the capacitor discharge described by the expoential model
• Record the time at which the capacitor voltage reaches half its initial value
• #### After the Activity

Students' will complete the Data Collection and Analysis Sheet and answer the questions listed in it.

Review student results

• As a class, discuss questions that appeared to be more challenging
• Re-teach concepts as necessary