Introduction to Electrostatics, Day 2
Lesson 2 of 6
Objective: Students will be able to identify which type of charging occurs and whether objects are conductors or insulators.
The goal of this lesson is to reinforce the ideas that students learned about in the jigsaw about the basics of electrostatics including types of charges, how an object becomes charged, conductors and insulators & types of charging. Students develop models for the different types of charging (SP2) and explain why conductor and insulators are related to electrostatics (SP6). The knowledge that students gain in this lesson leads to the use of Coulomb's Law which is present in standard HS-PS2-3.
To start out class, I have students take out their blank Guided Notes in their unit packets so we can formalize some of the concepts they worked with in their jigsaw in the previous class. The videos below show how I go through the notes.
To start, I discuss what electrostatics is, what electric charge is and the properties that the charge and charged particles have. I talk about the conservation of charge, that likes repel and opposites attract and about how the electron and proton are related. I also talk about what happens when charge transfers. Since these ideas are ones that students learned about during the jigsaw, I ask for student volunteers to help me with each section. They should be able to tell me about everything except for the definition of electrostatics so students supply a lot of the information and I formalize it in writing on my copy of the guided notes that they see on the projector screen.
Then I talk about the difference between conductors and insulators and how it helps us understand charge flow. And I finish the notes with explaining what grounding is.
After talking through the basics of electrostatics, I leave it to my students to learn from the online Conceptual Physics textbook about the different types of charging. To do this I have students complete the Charging Group Jigsaw as groups in the class. Since there are 3 types of charging and 7 table groups, I give 2 table groups the page about charging by conduction, 3 table groups charging by induction, and 2 table groups polarization. I hand out the corresponding slide from the Charging Group Jigsaw so students can find the answers to the questions as a group. I give them about 10 minutes as a group to read the text that goes with their type of charging to get the answers. I tell the students that they will share their knowledge for the rest of the class. I do this so the students have some ownership in this content. Also, this strategy breaks up the notes.
Types of Charging Notes
After the students work with their groups, I have the students share out and they put the notes in the types of charging section of the guided notes. To share out, I lead the discussion and ask the questions on the pages they used to complete the jigsaw and direct them toward one group at a time. I ask each group to provide information for one part of the type of charging. I make sure that each group is held accountable for their work by making sure they answer 1-2 questions per group. I start with the groups that did charging by conduction and students talk about charging by friction and charging by contact. After we define those, I show the John Travoltage simulation to show that when he rubs his feet on the carpet that is charging by friction and touches the doorknob that is charging by contact.
Then we move to the talking about charging by induction with those groups and about the two-sphere example and how something can be charged without even touching it. Finally we move to talking about polarization with the last groups and how it occurs within a neutral insulator when a charged object comes near it. I show the Sweater and Balloon simulation to show how when the balloon touched the wall it separates the charges on the wall. During this section students are to take notes based on what I write down from the groups' responses to the questions.
To end class, I have students move to the back to the room to the lab tables where I have provided various materials for different demonstrations to complete the Hands On Examples Chart for the different examples of charging. The first thing I ask my students to do is to find two conductors and four insulators in the bin. I give them about 3-4 minutes to actually see what is in the bin and to decide what their conductors and insulators are and write them on their group sheet, as seen below. Then I ask each group to hold up the 2 conductors that they found. Since there are only 2 conductors in the bin I can quickly tell if each group is able to determine the difference between the materials.
Then I lead the students through multiple situations where they have to determine as a group if which type of charge was happening and between which materials. The students complete the following demonstrations:
1. Paper and Plastic Spoon: Students rip up paper into small pieces. Then they rub the spoon with fur. They then put the spoon near the paper to see how many pieces of paper they can pick up without touching the table. [spoon & fur=conduction, spoon & paper=polarization]
2. "Electrophorus": The students have a metal pie tin with a styrofoam cup handle. I have them rub a styrofoam block with fur. Then I have the students hold the styrofoam cup handle and place the pie tin on the rubbed styrofoam. Students feel a small zap. [fur & styrofoam=conduction, finger & pie tin=conduction]
3. Sticky Tape: The students take two pieces of tape (with tabs so they can be pulled up) and put them on the table on top of each other. Then they rip them up together. Then they pull them apart. Then they bring the tapes together to see what happens (they repel). Then they bring each tape toward a straw and they both attract toward the straw and touch it. [tape & straw=polarization].
There are many other demonstrations that I could do, but I only chose 3 for time's sake. I like to complete this activity because it is an application of the concepts that the students learned during the guided notes. This flows well into the next lesson with the application of the charging examples into determining what charge an object becomes.