Download electric charge and static electricity

Name: Jenny Yang Content Area: Physical Science Grade Level: 8th grade Topic(s): Electric Charge and Static Electricity (90 minutes). Standards (Benchmarks): • Electric currents and magnets can exert a force on each other. • A charged object can be charged in one of two ways, which we call either positively charged or negatively charged. Two objects that are charged in the same manner exert a force of repulsion on each other, while oppositely charged objects exert a force of attraction on each other. Standards (SOLs): PS.1: The student will demonstrate an understanding of scientific reasoning, logic, and the nature of science by planning and conducting investigations in which a) Chemicals and equipment are used safely c) Conversions are made among metric units, applying appropriate prefixes; e) Numbers are expressed in scientific notation where appropriate j) Valid conclusions are made after analyzing data k) Research methods are used to investigate practical problems and questions l) Experimental results are presented in appropriate written form m) Models and simulations are constructed and used to illustrate and explain phenomena PS.11: Students will investigate and understand basic principles of electricity and magnetism. Key concepts include a) Static electricity, current electricity, and circuits b) Relationship between a magnetic field and an electric current c) Electromagnets, motors, and generators and their uses d) Conductors, semiconductors, and insulators Objectives (UKD’s): Understanding: • Students will understand how charges interact. • Students will understand how charges build up. Know: • Students will know that friction can cause electrons to be transferred from one object to another. These static electrical charges can build up on an object and be discharged slowly or rapidly. • Students will know that charges that are the same repel each other and charges that are different attract each other. • Students will know the four methods by which charges can redistribute themselves to build up static electricity: by friction, conduction, induction, and by polarization. • Students will know the vocabulary terms related to this lesson: electricity, electric force, electric field, static electricity, conservation of charge, friction, conduction, induction, polarization, and static discharge. Do: • Students will observe static electricity by moving an aluminum can with a balloon. • Students will observe electric forces by using pieces of tape. •
Students will construct a static detector. Topic/Essential Question: What makes something electrically charged? Materials & Resources: • Balloons • Craft sticks • Empty aluminum cans • Metal spoon • Piece of wool cloth • Plastic spoon • Aluminum foil • Pennies • Modeling clay • Aluminum foil • Clear plastic cup • Tape • Paper clips Safety Considerations: • Hand safety -­‐ Do not cut an object while holding the object in your hand • Sharp object safety -­‐ Use extreme care when handling all sharp and pointed instruments. -­‐ Cut objects on a suitable surface, always in a direction away from your body. -­‐ Be aware of sharp objects or edges on equipment or apparatus. Engage – Time Estimate: 5 minutes I will ask students if they can move an object without touching it. Students should answer that it is impossible. Then I will show them a youtube clip: http://www.youtube.com/watch?v=XlF2iPeWhI4. On this clip, this guy claims that he can move water bottles with his mind without using strings or magnets. After watching the clip, I will tell students that there is a way to move objects without physical touching them. Explore – Time Estimate: 25 minutes Students will be in their pre-­‐assigned lab groups that I made in the beginning of the year (students are grouped by random). Groups will be at one lab station for 10 minutes and will rotate. There are a total of two activities going on at the same time. During one activity, students will observe static electricity by moving an aluminum can with a balloon. In another activity, students will observe electric forces by using pieces of tape. See attachments: • Can You Move a Can Without Touching It • Tape Interactions Explain – Time Estimate: 25 minutes I will ask students to share their observations made from the two activities. I will be guiding them to make sure that they are making correct observations and to insure that there are no misconceptions. Also, I will make sure that students cover the important topics and vocabulary. After the discussion, students will be completing pre-­‐made notes that went along with the discussion. See attachment: • Electric Charge and Static Electricity Notes Extend – Time Estimate: 30 minutes During this time, students will be in their lab groups again and will be making a static detector. By making the static detector, students will observe ways in which objects can become electrically charged and how electric forces can cause objects to move. Although this activity is similar to one of the activities done in the exploration, students will observe that not all materials will make the detector move. This will help them in the next lesson because they will be learning about conductors and insulators. When doing this lab, they will have to remember what they have learned from what they explored and explained. See attachment: • Making a Static Detector Evaluate – Time Estimate: 5 minutes At the end of the lesson, students will complete a short assessment that will show me if they understand the material and if they are ready to move on to the next topic. See attachment: • I understand Electric Charge and Static Electricity Plans for Diversity: • ADD/ADHD: A variety of activities will be used and students will have opportunities to get up and move around the room throughout the class. • ELL: I will help students rewrite the key concepts and have them draw pictures. I will encourage students to use the dictionaries and write the vocabulary definitions in their first language next to the English definitions. • Auditory Learners: There will be discussions so that auditory learners will have an opportunity to hear the explanation. • Visual Learners: Students will be able to see visually what is happening when they do the activities and see how objects are being attracted or repelled. • Kinesthetic Learners: Students will be taking what they have learned and putting the words into actions when making the static detector. Connections: This is the first lesson of the unit. In this lesson, students will learn the basics of electricity and the charges of atoms. Students will need to have a firm understanding of this lesson because the later lessons will all be related. Can You Move a Can Without Touching It? (Teacher Copy – Answers are in Red) Have you ever wished that you could pull an object toward yourself without touching it? In this activity, you will use static electricity and observe what happens when objects that are statically charged interact with each other. Procedure: 1. Use the balloon to make the empty aluminum can move. Make sure you have statically charged the balloon. 2. Observe what happens. Think It Over: 1. From your observations, what can you infer about the relationship between the can and the balloon? The can will follow the balloon in either direction. 2. In order to cause the can to start moving, what must be acting on it? There is a force attracting the can to the balloon. 3. Moving the can required work. Recall that energy is the ability to do work or cause change. Can you infer where the source of energy came from to move the can? Explain. The energy used to rub the balloon was converted into a type of energy that could cause the can to move. Tape Interactions Procedure: 1. Cut three pieces of tape of approximately the same size. 2. Press two pieces of the tape onto your shirt. 3. Peel off the tape pieces and hold them near each other without them touching. 4. Hold one of the strips of tape removed from your shirt and hold it near the third strip. Think It Over: 1. What did you observe when holding the two pieces of tape removed from your shirt? The strips of tape repel each other. 2. What can you conclude about the charges on the tape based on this reaction? Both pieces of tape have the same charge. 3. What did you observe about the strip of tape removed from your shirt and the strip of tape that was not in contact with your shirt? The strips of tape attract each other. 4. What can you conclude about the charges on the tape based on this reaction? The strips are oppositely charged because they attract one another. Electric Charge and Static Electricity Notes (Teacher Copy – Answers are in Red) How do charges interact? • Misconceptions: Force fields exist only in science fiction stores – FALSE. • A force field exists around any object that repels or attracts other objects. • Atoms contain charged particles called electrons and protons. • The charge on a proton is positive (+). • The charge on an electron is negative (-­‐). • If two electrons or two protons come together, they push each other apart. • If a proton and an electron come close together, they attract one another because they have opposite electric charges. Charges that are the same repel each other. Charges that are different attract each other. • The interaction between electric charges is called electricity. • The force between charged objects is called electric force. • Electric field: A region around a charged object where the object’s electric force is exerted on other charged objects. • Electric fields and forces get weaker the farther away they are from the charge. How does charge build up? • Misconception: Charging by friction involves most or all of the atoms in the objects that are rubbed together – FALSE. • Charging by friction involves only a small fraction of atoms on an object. • The buildup of charges on an object is called static electricity. • In static electricity, charges build up on an object, but they do not flow continuously. • The rule that states that charges are neither created nor destroyed is conservation of charge. •
Destroying or creating its own electrons cannot charge an object. If one object loses electrons, another object must pick them up. There are four methods by which charges can redistribute themselves: 1. Friction: transfer of electrons from one uncharged object to another by rubbing the objects together (ex: rubbing your hair with a balloon). 2. Conduction: transfer of electrons from one object to another by direct contact (ex: a positively charged metal spoon touching a neutral aluminum plate. The neutral plate will now be charged). 3. Induction: electrons reacting to the electric field of a charged object without touching the object itself (ex: when a metal object is close to a negatively charged object, electrons are repelled by the field and move away from it. The close end of the metal object becomes positively charged, and the far end becomes negatively charged). 4. Polarization: electrons reacting to the electric field of a charged object without touching the object itself (ex: bits of paper, electrons move only within their own atoms. The electrons react to electric fields, resulting in individual atoms having charged ends that are attracted to charged objects). We will learn later why the materials being used matters for induction and polarization • Charges don’t transfer between objects in polarization or induction, so neither method changes the overall charge of objects; only parts of objects end up charged in opposite ways. • The loss of static electricity as electric charges transfer from one object to another is called static discharge (ex: lightening bolts). Making a Static Detector (Teacher Copy – Answers are in Red) In this activity, you will build a device that will allow you to observe the effects of static electricity. As you conduct the investigation, remember that like charges repel, while opposite charges attract. Procedure: 1. First bend a paper clip so that it forms a straight line with a hook on the end. Insert the paper clip through the hole in the cup so that the hooked end is inside the cup and the straight end extends through the bottom of the cup. Use clay on the outside of the cup to hold the paper clip in place. Hold the paper clip by the tip of the straight end. 2. Stick a ball of aluminum foil onto the straight end of the paper clip so that it is between the bottom of the cup and your hand. 3. Bend the aluminum foil strip in half and shape it so it forms an upside-­‐down “V.” Then, pace the strip on the hooked end of the paper clip so that the two halves of the strip hang down on both sides of the hook. 4. In your lab groups, brainstorm a procedure that will allow you to move the aluminum strip inside the cup without touching the strip or shaking the cup, and using only the materials provided. List the steps for your procedure on a separate sheet of paper. Rub the balloon on a student’s head, thereby giving the balloon an electric charge, and then moving the charged balloon toward the foil ball, which is connected to the foil strip by the paper clip. 5. Summarize the results of your experiment If the experiment is successful, moving the balloon toward the foil ball will cause the two halves of the aluminum strip to move apart from each other. 6. If your experiment succeeded, explain why you were able to move the aluminum strips inside the cup. How is this related to static electricity? Rubbing the balloon on my hair gave the balloon a negative charge. Because like charges repel, moving the charged balloon toward the foil ball caused negative charges in the foil ball to move through the paper clip to the foil strip. Because the two halves of the strip had the same charge, they repelled. 7. If your experiment did not succeed, identify the likely source(s) of your error(s), and explain how you could correct those errors. Likely source of error include touching the foil ball with the balloon, touching the balloon before moving it beside the foil ball, and causing the static detector to come in contact with the ground. Any of these errors will cause the negative charges to leave the balloon or the static detector before they have a chance to affect the aluminum strip. 8. Write a question that could be answered by using your static charge detector to collect data. What would happen to the aluminum strip of I tested an object carrying a positive charge rather than a negative charge? What would happen if I replaced the aluminum strip with a strip made from a different material, such as paper or rubber. I understand Electric Charge and Static Electricity (Teacher Copy – Answers are in Red) 1. When charges are the same, they repel each other. 2. When charges are different, they attract each other. 3. What are the four methods by which charges can redistribute themselves to build up static electricity? Friction, Induction, Conduction, and Polarization. 4. What is an example of an object building static electricity by friction? Rubbing a balloon on your hair. 5. On a scale from 1 – 10 (1 – I have no idea what’s going on, 10 – I can teach this to my parents) how comfortable are you with this material?