Name: Jenny Yang Content Area: Physical Science Grade Level: 8th grade Topic(s): Circuits & conductors, semiconductors, and insulators (90 minutes). Standards (Benchmarks): • Materials vary in how they respond to electric currents, magnetic forces, and visible light or other electromagnetic waves. • Electric currents and magnets can exert a force on each other. • Electrical circuits require a complete loop through which an electrical current can pass. • Energy appears in different forms and can be transformed within a system… Electrical energy is associated with an electric current in a circuit… • Energy can be transferred from one system to another (or from a system to its environment) in different ways: … 3) electrically, when an electrical source such as a battery or generator is connected in a complete circuit to an electrical device; … Standards (SOL): 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; 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; and n) current applications of physical science concepts are used. 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 conductors differ from insulators. • Students will understand what a circuit is made of. Know: • Students will know that the atoms in conductors have loosely bound electrons that can more freely. • Students will know that electrons in insulators cannot move freely among atoms. • Students will know that a conductor is a material that transfers an electric current well. An insulator is a material that does not transfer an electric current. A semiconductor is in-­‐between a conductor and an insulator. • Students will know that all electric circuits have these basic features: devices that run on electrical energy, sources of electrical energy, and conducting wires. •
Do: •
Students will know the vocabulary terms for this lesson: conductor, insulator, semiconductors, and series circuit, parallel circuit, open circuit, closed circuit. Students will identify examples of materials that are good conductors, semiconductors, and insulators. Students will construct and compare series and parallel circuits. •
Topic/Essential Question: How do electric circuits work? Materials & Resources (For each lab group): • Battery, D-­‐cell, in holder • Light bulbs with holder (x2) • Wires with alligator clips (x4) • Rubber band, • 10-­‐cm strings • 10-­‐cm copper wires • 10-­‐cm aluminum wires • 25-­‐cm lengths of bell wire (x2) Safety Considerations: • 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. • Electrical safety -­‐ Do not use equipment with frayed electrical cords or loose plugs. -­‐ Fasten electrical cords to work surfaces by using tape. -­‐ Do not use electrical equipment near water or when clothing or hands are wet. -­‐ Hold the plug housing when you plug in or unplug equipment. -­‐ Be aware that wire coils in electrical circuits may heat up rapidly. Engage – Time Estimate: 5 minutes Students will watch a video clip about electric circuits on youtube. It’s a catchy song created to the tune Pumped Up Kicks. The song is about circuits, but it also has a nice preview about magnetism, which will be tomorrow’s lesson. http://www.youtube.com/watch?v=y3yoXh94Vp0. Explore – Time Estimate: 35 minutes Students will be in their pre-­‐assigned lab groups that I made in the beginning of the year (Note: There are 20 students in this “hypothetical” class and there will be a total of four lab groups with five students in each group). Lab groups will be completing these two different labs on their own. They will have 30 minutes to finish both labs. During the parallel and series circuit lab, students will build each circuit and then compare the brightness of light bulbs and draw conclusions about the voltage in each circuit. Also they will observe what happens to the lights, as some are unscrewed. During the conductors and insulators lab, students will explore electrical conductors and insulators by identifying which materials (string, rubber bang, copper wire, aluminum wire) are conductors and which are insulators. See attachments: • Compare these two Circuits • Conductors and Insulators Explain – Time Estimate: 20 minutes I will ask students to share their observations made from the two activities. I will make sure that students cover the important topics and vocabulary. During this time, students will be completing pre-­‐made notes that will go along with the guided discussion. See attachment: • Electric Circuits Notes Extend – Time Estimate: 25 minutes During this time, students will be playing a review game called Trashketball. Rules to the game will be on the powerpoint. See attachment: • Circuits Trashketball 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 Circuit 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: The series and parallel circuits lab will help students to visually see the circuits. • Kinesthetic Learners: The review game will give students the opportunity to move around the classroom and the lab activity will provide students with a “hands-­‐on” experience. Connections: This is the third lesson of the unit. In this lesson, students will learn about series and parallel circuits. Also, students will learn about conductors and insulators. In the previous lesson, students learned about the flow of electricity, now they will learn about ways that electricity flow can be stopped and how some materials doesn’t allow flow of electricity. I thought it would be a good idea to teach both these concepts on the same day because as students are creating series and parallel circuits, they can use different conducting materials and insulating materials to see if the light bulbs will light. Compare these two Circuits (Teacher Copy – Answers are in Red) Procedure: 1. Construct a circuit that resembles the diagram below: 2. Construct another circuit that resembles the diagram below: 3. Write down your observations of the light bulbs of each circuit. In the series circuit, the light bulbs were dimmer. This indicates that the voltage was divided between the two light bulbs. However, because the current flows through one loop, the current remains the same through the entire circuit. In the parallel circuit, the light bulbs were brighter than the series circuit. There are multiple paths around which current flows, the current divides up through the different paths. Also, in a parallel circuit, the light bulbs receive the most voltage. 4. What happens if you unscrew one of the light bulbs from the first circuit? What about the second circuit? Explain. If you unscrew one of the light bulbs from the series circuit (first circuit) then the other light bulb will go off because there is only one path through which it could run. If you unscrew one of the light bulbs from the parallel circuit (second circuit) then the other light bulb will stay one because there are more then one path for electricity to follow. Conductors and Insulators (Teacher Copy – Answers are in Red; Students will not be given the pre-­‐made data table) Procedure: 1. Look at the materials and predict which materials should conduct electricity and which should be insulators. 2. Construct the circuit below and brainstorm on how you can test each material as a conductor or an insulator. 3. Create a data table to show your hypothesis and the results. Materials Hypothesis Results Rubber band Insulator String Insulator Copper wire Conductor Aluminum wire Conductor Bell wire Conductor Note: The students will not be given this pre-­‐made data table Think it Over: 1. Did your observations support your predictions? Explain. 2. Based on your results, predict whether a tire, a scarf, and a penny would be conductors or insulators. Conductor: penny Insulators: tire and scarf 3. Why do extension cords have rubber or plastic material covering them? Extension cords have rubber material covering them because rubber is an insulator so it keeps the conductors from touching, and it prevents accidental contact with other conductors of electricity. Electric Circuits Notes (Teacher Copy – Answers are in Red) How Do Conductors Differ From Insulators? • A conductor is a material through which charge can flow easily. • Metals are good conductors, which is why current-­‐carrying wires are usually made of metal. • Wires are surrounded by insulators because materials like rubber do not allow charges to flow. • The difference between conductors and insulators comes from how strongly electrons are attached to atoms. • The atoms in conductors have loosely bound electrons that can move freely. • Electrons in insulators cannot move freely among atoms. Semiconductors • Semiconductor is a solid material whose electrical conductivity at room temperature is between that of a conductor and that of an insulator. • At high temperatures its conductivity approaches that of a metal, and at low temperatures it acts as an insulator. • In a semiconductor, there is a limited movement of electrons. • Some examples of semiconductors are silicon and germanium. • Transistors are semiconductor devices made from silicon, and other semiconductors. They are used to amplify electrical signals (in stereos, radios, etc) or to act like a light switch turning the flow of electricity on and off. • A diode is a semiconductor device that acts like a one-­‐way valve to control the flow of electricity in electrical circuits. Solar cells are made of semiconductor diodes that produce direct current (DC) when visible light, infrared light, or ultraviolet energy strikes them. • Light emitting diodes (LED) emit visible light or infrared radiation when current passes through them. An example is the transmitter in an infrared TV remote or the lighting course behind the screen in an LED TV or notebook computer screen. What Is a Circuit Made Of? • Everything that uses electricity contains a circuit. • All electric circuits have the same basic features: devices that are run by electrical energy, sources of electrical energy, and conducting wires. Series Circuits • If all the parts of an electric circuit are connected one after another along one path, the circuit is called a series circuit. • A series circuit has only one path for the current to take. • If a light bulb burns out in a series circuit, the other lights go out as well. • Another disadvantage of a series circuit is that the light bulbs in the circuit become dimmer as more bulbs are added. Parallel Circuits • In a parallel circuit, different parts of the circuit are on separate branches. • There are several paths for current to take. If a light burns out charges can still move through the other branches. The other bulbs remain lit. •
When you add a branch to a parallel circuit, the overall resistance decreases. (Remember that for a given voltage, if resistance decreases current increases). The additional current ravels along each new branch without affecting the original branches. So as you add branches to a parallel circuit, the brightness of the light bulbs does not change. Kings and Queens of Circuits Rules: • Class will be divided into four teams • Each team will answer one question at a time • If your team answers correctly, you get a point and you also get a chance to get more points by making the ball into the trash can • If your team answers incorrectly, the next team will get a chance to answer the question for a point BUT will not be able to shoot for additional points • Every person in each team will get a chance to answer the questions • The team with the most points at the end will receive a special prize
Electric Circuits (Underlined words/phrases will be blank on student copy) Circuit A Circuit B 1. Which circuit is a series circuit? Circuit B 2. Which circuit is a parallel circuit? Circuit A 3. What happens to the bulbs in Circuit A, if one of the bulbs goes out? The other two remains on. 4. What happens to the bulbs in Circuit B, if one of the bulbs goes out? The other bulbs will go out. 5. CIRCLE all the conductors and SQUARE all the insulators. (Silver) (Bronze) (Dirty water) (Copper) [Plastic] [Pure water] [Rubber] [Diamond] (Aluminum) [Air] (Iron) [Glass]