Introduction:
The third electrostatic lab/activity uses the Electrophorus to reinforce charging by friction, charging by conduction, and polarization of charge and to introduce variations of charging by induction.

Timing: This lab/activity should take about an hour and a half to complete (without building the Electrophorus).

Acknowledgments: This lab is built loosely around the Exploratorium’s Summer Institute’s – Electrophorus

Group Size: Small groups
 

Learning Objectives:
The objective of this lab/activity is to:
a) Introduce the following key concepts:
-Charging by Induction
-Grounding
b) Reinforce the following concepts from the previous lab work:
-Charging by friction
-Polarization of charge
-Charging by conduction
 

Guiding Question:
What are the techniques to electrically charge an object and how does the type of charge produced vary with each technique?
 

Materials:
Each lab group should have three Electrophorus devices, two Styrofoam plates, two neon glow tubes.
- Electrophorus devices are easy to build and a handout on constructing them has been attached to this lesson. Make sure to reinforce the tape connecting the insulating cup and the pie tin between classes.
- Neon glow tubes are low power, high voltage lamps and can be found by doing an internet search or you can buy them from: http://www.surplussales.com/Bulbs-Incan-Panel/BulbsNeon.html - Buy either the Neon Lamp with Resistor?115 vac or the Neon Lamp?90 vac. The resistor version is nice, but you need a bit more juice to fire the bulb, but you won’t blow as many.
 

Procedures:
Electrophorus devices work best with low humidity, but still can have decent results with moderate humidity. Pick the experiment day accordingly. Having students build the Electrophorus devices the day before helps. The construction of the electrophorus devices should take no more than 15 minutes.
Part 1: As students follow the procedure on the lab sheet, the instructor should make sure students:
- are not accidentally grounding the Electrophorus by touching the pie tin.
- are only touching one connector of the neon bulb to the Electrophorus.

Part 2: As students follow the procedure on the lab sheet, the instructor should make sure students are following the Part 1 precautions.

Part 3: As students follow the procedure on the lab sheet, the instructor should make sure students are following the Part 1 precautions and:
- are touching the uncharged Electrophorus at the farthest point away from the charged Electrophorus.

Part 4: As students follow the procedure on the lab sheet, the instructor should make sure students are following the Part 1 precautions and:
- are very careful not to ground either of uncharged Electrophori when separating them.

Part 5: As students follow the procedure on the lab sheet, the instructor should make sure students are following the Part 1 precautions and:
- put their finger on the far side of the uncharged Electrophorus.
- only place their finger on and remove their finger from the uncharged Electrophorus while the charged Electrophorus is near, but not in contact.
 

Assessment:
Throughout the first 5 sections of the experiment, students will complete questions and charge distribution diagrams based on their experiences and gained knowledge. The instructor should correct any inaccuracies in student answers and diagrams during the actual experiments. Since the answers and diagrams have already been checked, these should be graded for completion. The last section is a 10-question assessment of the lab experiences and gained knowledge. These should be graded for correctness.
 

Answer Key or Rubric:
See Answer Key attachment below. Many of the the diagrams will not paste in properly.


 

Attached Files:

Word Answer Key

PDF Answer Key

Electrophorus Lesson Plan

Non-profit Tax ID # 203478467