Unit Five Organizer: Charge! (Approximate Time: Seven Weeks)

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1 The following instructional plan is part of a GaDOE collection of Unit Frameworks, Performance Tasks, examples of Student Work, and Teacher Commentary. Many more GaDOE approved instructional plans are available by using the Search Standards feature located on GeorgiaStandards.Org. Georgia Performance Standards Framework Physical Science Grades 9-12 OVERVIEW: Unit Five Organizer: Charge! (Approximate Time: Seven Weeks) This unit is built on the understanding that electricity involves charged particles and that it may build up (static) or flow (current). This understanding is expanded to include the relationship of electricity to magnetism and to conductivity of solutions. Students will investigate the properties of static and current electricity as well as applications of electromagnetism. STANDARDS ADDRESSED IN THIS UNIT Focus Standard: SPS10. SPS6. Students will investigate the properties of electricity and magnetism. a. Investigate static electricity in terms of friction induction conduction b. Explain the flow of electrons in terms of alternating and direct current. the relationship among voltage, resistance and current. simple series and parallel circuits. c. Investigate applications of magnetism and/or its relationship to the movement of electrical charge as it relates to electromagnets simple motors permanent magnets Students will investigate the properties of solutions. a. Describe solutions in terms of conductivity Physical Science Grades 9-12 Charge! Page 1 of 6

2 STANDARDS ADDRESSED IN THIS UNIT (continuation) Supporting Standards: SPS8. Students will determine relationships among force, mass, and motion. b. Apply Newton s three laws to everyday situations by explaining the following: Inertia Relationship between force, mass and acceleration Equal and opposite forces SPS4. Students will investigate the arrangement of the Periodic Table. a. Determine the trends of the following: Number of valence electrons Types of ions formed by representative elements Location of metals, nonmetals, and metalloids ENDURING UNDERSTANDINGS Students will understand that: Electric current is the result of the motion of charged particles across a conductor. Friction forces can cause the accumulation of an unbalanced amount of charged particles on the surface of an object. The voltage created between two objects due to the presence of an unbalanced charged may create an electric spark or shock. Electrons can be transferred from one charged conductor to another by physical contact. When a charged object is moved into proximity to a conductor, the conductor is charged by induction. An electric current requires a complete circuit and a voltage source. The amount of current that flows in a circuit depends on both the resistance and the voltage of the source. In a series circuit the same amount of current flows through all the components. In a parallel circuit the voltage drop across each component is equal and equal to the voltage of the power source. In a direct current circuit the electrons flow in only one direction. In an alternating current the motion of the electrons alternates back and forth due to the changing polarity of the voltage source. Charges in motion generate magnetic fields. Variable magnetic fields induce currents in a circuit. A moving electric charge, or current, in a magnetic field experiences a force. Page 2 of 6

3 ESSENTIAL QUESTIONS: What does it mean when something is electrically charged? How can object become electrically charged? Why can small birds sit on high-voltage power lines? Why does striking a magnet with something hard weaken its magnetism? Why is an alternating current necessary for a motor to work? Why is an electromagnet more powerful when it possesses an iron core? What characteristics of the material make it a good conductor or insulator? Why are insulators attracted to charged objects? Why is alternating current commonly used in household applications? How do electric generators work? How are electric generators and motors different and alike? How do transformers work? How is an electromagnet made? CONCEPTS: Friction, conduction, induction, alternating current, direct current, voltage, resistance, current, series circuits, parallel circuits, electromagnet, permanent magnets, solutions, conductivity, valence electrons, ions, metals, nonmetals, metalloids, representative elements, force LANGUAGE: Acceleration Alternating current Charge Conduction Conductivity Current Direct current Electricity Electromagnet Force Friction Induction Ions Metalloids Metals Motor Nonmetals Parallel circuit Permanent magnet Representative elements Resistance Series circuit Solutions Valence electrons Velocity Voltage Work Page 3 of 6

4 MISCONCEPTIONS Voltage flows through a circuit. Voltage is energy. High voltage by itself is dangerous. Charges move by themselves. Resistors consume charge. Electrons move quickly (near the speed of light) through a circuit. Current is the same as voltage. Current gets used up as it flows through a circuit. PROPER CONCEPTIONS Voltage is the difference of electrical potential between two points of an electric circuit. It is the amount of current passing through the body that determines the damage that an electric shock may produce. How much damage certain voltage is determined by the low conductivity of the dry human skin. If skin is wet or if there are wounds, then even voltages far below 40 V can be lethally high. Various safety organizations consider greater than 50 V to be dangerous. Voltages above this range are capable of producing heart fibrillation if they produce electric currents in body tissues which happen to pass through the chest area. On the other hand, voltages above approximately 500 V have a natural defibrillating effect, so sometimes a higher voltage can be safer than a lower voltage, though by no means safe. A power source (battery) is necessary to supply the energy to move a charge from its low energy, low potential terminal to the high energy, high potential terminal. Collisions of charge carriers in an electric circuit with the conducting elements of that circuit result in a loss of energy not a loss of charges. Most the electrical energy possessed by a charge carrier is lost when it passes through an electrical device (resistors, light bulbs, wires, etc.). It is because of this energy loss that the electric potential of a charge carrier decreases as it traverses the external circuit. Electrons actually move quite slowly at speeds of a few centimeters/minute. The speed at which electrons move is called the drift velocity. It is the energy in the circuit which flows fast not the electrons. Current is the flow of electric charge, voltage is the difference of electrical potential between two points of an electric circuit. Electric circuits are all about energy, not charge. The charge is simply the medium which moves the energy from location to location. Page 4 of 6

5 Current is an excess charge. One Stop Shop For Educators MISCONCEPTIONS The bigger the battery, the more voltage. Power and energy are the same thing. Batteries create energy out of nothing. North and south magnetic poles are the same as positive and negative charges. Water in dams causes electricity. In AC current, charges move all the way around a circuit and all the way back. Electrical companies supply the electrons for your household current. The electric energy in a circuit flows in a circle. Page 5 of 6 PROPER CONCEPTIONS Current is the flow of electric charge The size of a battery does not determine the voltage of the battery. The voltage of a battery is depends of the amount of chemical energy that is transformed to electrical energy. Inside the battery itself, a chemical reaction produces the electrons. The speed of electron production by this chemical reaction (the battery's internal resistance) controls how many electrons can flow between the terminals. Power is the measure of how much energy is being used on a set amount of time. Batteries work by packing a collection of reactive chemicals inside. These chemicals undergo an oxidation-reduction reaction that produces energy. This energy-producing reaction is capable of pumping the charge through the battery from low energy terminal to high energy terminal and establishing an electric potential difference across the external circuit. North and south magnetic poles are created by the alignment of the spins of electrons on a particular material. Charge is a property of matter. Electrons are negatively charged while protons are positively charged. Water does not cause electricity. It is motion of water through a turbine that transforms the kinetic energy of the water into electrical energy. In AC circuits electrons do not really move at all, instead they sit in place and vibrate. Electric companies sell energy (kw hr is a unit of energy. This is the unit on one s electric bill). Electric energy flows from the power source to the dissipating element like a resistor or a light bulb for example, where it is turned into another form of energy, heat or light for these examples. This is a one way flow, the source loses energy and the resistor or light bulb gain energy. Electric energy is composed of waves traveling along the electrons inside the wires and the energy itself is stored on the electromagnetic fields around those electrons.

6 EVIDENCE OF LEARNING: By the conclusion of this unit, students should be able to demonstrate the following competencies: Culminating Activity: Following the guidelines of the project, students will construct a lightweight two story electrical house in which they will construct separate series, parallel, and complex circuits. The house will consist of two stories. Each story will contain at least two rooms. Each individual room will be illuminated by its own light. There should be a front door and a porch light. Your house circuits should be able to light the first floor lights and the porch light separately from the second floor lights and the door bell. Requirements for The Electric House The house must have at least one series circuit consisting of a switch and at least two Christmas tree lights powered by a nine volt battery. The house must have at least one parallel circuit consisting of a switch and at least two Christmas tree lights powered by a second nine volt battery. The house must have at least one complex circuit consisting of a switch, at least two Christmas tree lights, and one doorbell (or buzzer) powered by a third nine volt battery. Materials for The Electric House At least six Christmas tree light bulbs. Three nine volt batteries. Three switches. (or some combination) May be made out of paperclips and wire. Two average size rolls of insulated wire (it is helpful to have one red and one black roll). Suggestion: if you are using a strad of Christmas tree lights (the small ones), there is enough extra wire! It works perfectly. Doorbell or buzzer. Suggestion: use a Piezo buzzer available at electronics stores. Foam-core or card board. Poster board is too flimsy. Suggestion: You can cut apart cardboard boxes. Page 6 of 6