ELECTRICITY AND MAGNETISM CREEKSIDE HIGH SCHOOL.

Transcription

1 STEP-UP 2008 LESSON PLAN UNIT: TIME: ELECTRICITY AND MAGNETISM 8 WEEKS CLASS LEVEL: HIGH SCOOL PHYSICS. GRADES: 11 & 12 NAME: SCHOOL: ANITA NAIR CREEKSIDE HIGH SCHOOL. 07/21/2008.

2 PROBLEM:! "ow is energy stored in a battery0! 1hat conditions make it advantageous to connect lights on a parallel configuration instead of a series configuration0! "ow does the electric energy generated in a power plant reach your home0! 1hy do some materials make good magnets and others do not0 ABSTRACT: The unit starts with a study of static electricity and quickly moves towards the understanding of charge and current. The energy conservation theorem is used to help explain the behavior of current and voltage in parallel and series circuits. At the same time, an elemental discussion of how matter responds to the presence of a current is given with the introduction of the concept of resistance. The next step is understanding the connections between electricity and magnetism. First the student will study the macroscopic effects that magnets have on each other and on magnetic materials. Second, the student will study the connection between a moving charged particle and the presence of a magnetic field. ACTIVITIES: There are two culminating activities in this unit. Firstly, the student is asked to apply the main concepts developed throughout the unit and to explain the techniques used to make discoveries through a series of controlled, laboratory experiments. The second culminating activity is the presentation of a research paper that describes how the fundamental understandings acquired throughout the unit impact the technology that surround us. STANDARDS ADDRESSED IN THIS UNIT: FOCUS STANDARDS: SP5: Students will evaluate relationships between electrical and magnetic forces.

3 SP3: Students will evaluate the forms and transformation of energy.! Students will analyze and measure power. SUPPORTING CONTENT STANDARDS: SP3: Students will evaluate the forms and transformations of energy. CHARACTERISTICS OF SCIENCE STANDARDS: SCSh1: Students will evaluate the importance of curiosity, honesty, openness, and skepticism in science. SCSh2: Students will use standard safety practices for all classroom laboratory and field investigations. SCSh3: Students will identify and investigate problems scientifically. SCSh4: Students will use tools and instruments for observing, measuring, and manipulating scientific equipment and materials. SCSh5: Students will demonstrate the computation and estimation skills necessary for analyzing data and developing reasonable scientific explanations. SCSh6: Students will communicate scientific investigations and information clearly. THE NATURE OF SCIENCE STANDARDS: SCSh7: Students will analyze how scientific knowledge is developed. SCSh8: Students will understand important features of the process of scientific inquiry. READING STANDARD: SCShO: Students will enhance reading in all curriculum areas by:! Reading in all curriculum areas Read technical texts related to various subject areas.! Building vocabulary language knowledge.! Establishing context.

4 ENDURING UNDERSTANDING: 1 The electric force exerted by a charged particle on another is proportional to the product of their charges and inversely proportional to the square of the distance between them. 2 The higher the potential difference between two points in a circuit the greater the amount of current passing through it as long as the resistance is kept constant. 3 Electric potential difference is the difference in electric potential between two different locations within an electric field. 4 In a parallel circuit the voltage across the parallel elements is the same and the current passing through each one is inversely proportional to the ratio of their resistances. 5 In a series circuit the current passing through all the elements is the same. 6 In a series circuit the total resistance of the circuit is equal to the sum of the resistances of the individual elements of the circuit. 7 The sum of voltage dropped on a closed loop of a circuit is zero. 8 Magnetic fields are created by electric currents and can be macroscopic like the current through a wire or microscopic like the one created by the moving of electrons in their atomic orbits. O A magnetic field affects the trajectory of a charged particle moving through it. 10 A variable magnetic field will induce an electric current and a variable current will induce a magnetic field. 11 Transformers are used to change the voltage in a circuit by stepping it up or down. MISCONCEPTIONS: An electromagnet must have an iron core.! Warger magnets are stronger than smaller ones.! Magnets can be used to separate metals from non metals.! Batteries are a source of charge.! Electricity is a form of energy.! Current is a type of electrical energy.

5 PROPER CONCEPTIONS:! An electromagnet is a wire coiled around a cylinder. It may or may not have an iron core.! The strength of a magnetic force generated by a magnet depends oupon the number of turns, current, and core material.! Some metallic materials are not magnetic. Therefore, magnets cannot always be used to separate metals from non metals.! A battery creates a potential differencex it does not produce a charge.! Electricity is the effect of the apparent motion by an electric current. Current is produced by the apparent motion of electrons along a conductor. EVIDENCE OF LEARNING: By the conclusion of this unit, students should be able to demonstrate the following competencies: Culminating Activity: E"ectric )ie"d "o to% mulations6e/index.htm &ith this sim+lation/ yo+ can investigate several topics dealing with electric fields created by point charges. <ere are some things to consider. a. "ow does the pattern change as you increase the magnitude of the charge0 More field lines. 7 pts b. "ow does it change when you keep the magnitude the same and reverse the sign0 Field lines change 180? 7 pts 2. Yote how the field lines get further apart the further away from the charge they

6 are. 1hat does this tell you about how the magnitude of the electric field changes with distance from a charge0 Field strength decreases as distance from charge increases. 7 pts 3. Add a second charge by sliding the Charge 2 button left or right. Click on the Zshow net electric field[ box. Adjust the charges so that, net electric field is zero. 1here is the electric field equal to zero0 At the origin, 0,0 7 pts 4. Set one charge to +4!C and the other to +1!C. a. 1here on the line joining the two charges is the net field equal to zero0 Along the x-axis closer to the 1?C charge. 7 pts b. If one charge is +4!C and the other is ]1!C, where on the line joining the two charges is the net field equal to zero0 Nowhere 7 pts ^uestions: 1. Do electric field lines start or end at a positive charge0 1hat about a negative charge0 Start at positive end at negative 7 pts 2. 1hen there are two charges, the charges exert forces on one another. a. Under what conditions do the charges attract one another0 When the charges are opposite 7 pts b. Under what conditions do the charges repel0 When the charges are the same 7 pts c. "ow does the force on a charge depend on the magnitude of the charge0 As charge increases, force increases 7 pts 3. 1ith two charges, if one charge has a larger magnitude than the other, which charge experiences more force0

7 Both experience the same force. 7 pts Title: MAGNETISM Purpose Investigate the properties of permanent magnets. Materials Magnetic compass, 2 nails, 2 bar magnets, iron filings, plastic sleeve with sheet of paper, wires, battery, paper clips Procedure A. Compass and Magnet Check 1. Check the compass by holding the south end of the bar magnet near the compass. The north end of the compass needle should point towards the bar magnet. B. Induced Magnetism 1. Rub a nail against the bar magnet. 2. Bring the nail near the compass. 3. Check the nail to see if it has both, a north and a south pole. C. Magnetic Field - one magnet 1. Place a bar magnet inside the plastic sleeve on top of the sheet of paper. 2. Sprinkle iron filings on the sleeve. 3. Gently tap the paper with your finger. 4. Make a drawing below of any pattern that appears: Y S 5. Explore the magnetic field by following the pattern lines with the compass. 6. Draw the orientation of the compass needle in six different places around the bar magnet. D. Magnetic Fields - north to north 1. Repeat part C with both magnets under the sleeve. Place the magnets so the north poles are facing each other. 2. Make a drawing below of any pattern that appears:

8 E. Magnetic Fields - north to south 1. Repeat part C with both magnets under the sleeve. Place the magnets so the north pole is facing the south pole. 2. Make a drawing below of any pattern that appears: F. Electromagnet 1. Wrap as many turns of wire around the nail. Connect the ends of the wire to the battery. How many paper clips can you pick up? 2. Remove the paper clips and bring a compass near the electromagnet. What happens to the compass? Analysis 1. Was magnetism induced in the nail when it was rubbed on a magnet? Explain what happened to the domains of the nail. 2. How many poles were induced in the nail?

9 3. Where, around a magnet, are the magnetic field lines most concentrated? 4. What does a wire become when current moves through it? Purpose: Compare series and parallel circuits Define series circuit: Click on ZPop upsb to turn them on. Click on ZVisualizeb so you can see the current flow. Click on the hand and select Building a series circuit. Click Oe. Click on clear. Yow, build your own circuit with six light bulbs in series. Draw a schematic diagram of the circuit using the symbols from your notes. If one light bulb is removed, what will happen to the current0 Test your answer. 1hy does this happen (hint: look at the text to the left of the circuit)0 Place the hand over the battery. 1hat is the potential difference in the battery0 Place the hand over the light bulbs. 1hat is the resistance of the light bulbs0

10 Define parallel circuit: Click on the hand and select Building a parallel circuit. Click Oe. Click on clear. Yow, build your own circuit with four light bulbs in parallel. Draw a schematic diagram of the circuit using the symbols from your notes. If one light bulb is removed, what will happen to the current0 Test your answer. 1hy does this happen (hint: look at the text to the left of the circuit)0 Place the hand over the battery. 1hat is the potential difference in the battery0 Place the hand over the light bulbs. 1hat is the resistance of the light bulbs0 Clear the board, click on the hand and select ZOhm[s Waw.b Press ZOe.b Wook at the voltmeter. 1hat is the potential difference across the light bulb0 Wook at the ammeter. 1hat is the current going through the light bulb0 1rite the formula for resistance. Solve for the resistance of the light bulb. Electric Field "o to% mulations6e/index.htm &ith this sim+lation/ yo+ can investigate several topics dealing with electric fields created by point charges.

11 1. a. <ere are some things to consider. The default settings, with one charge set to zero and the field vectors off, allow you to focus on the electric field from a single point charge. Observe the field line pattern as you change the magnitude and sign of charge 1. (change the magnitude and sign by sliding the charge 1 button left and right) "ow does the pattern change as you increase the magnitude of the charge0 b. "ow does it change when you keep the magnitude the same and reverse the sign0 2.Yote how the field lines get further apart the further away from the charge they are. 1hat does this tell you about how the magnitude of the electric field changes with distance from a charge0 3. Add a second charge by sliding the Charge 2 button left or right. Click on the Zshow net electric field[ box. Adjust the charges so that, net electric field is zero. 1here is the electric field equal to zero0 4.Set one charge to +4!C and the other to +1!C. a. 1here on the line joining the two charges is the net field equal to zero0 b. If one charge is +4!C and the other is ]1!C, where on the line joining the two charges is the net field equal to zero0

12 CONCLUSION: By the end of the unit the students should be able to complete the given task and submit their research work. Research one of these scenarios related to the usefulness of magnetic fields and electrical energy. Prepare a report on your research. a. A huge debate raged in the 1880[s and 18O0[s between proponents of alternating current and those who advocated direct current to provide the electricity to the U.S. "ow were Thomas Edison and George 1estinghouse involved in this controversy0 1hat advantages and disadvantages did each side claim0 1hat uses of electricity were anticipated0 1hat did all of this have to do with Yiagara Falls0 If you had been asked to decide the debate, which alternative would you have favored0 1hy0 b. Research the history of telecommunication. 1ho invented the telegraph0 "ow does it work0 1hat was its significance both historically and economically0 1ho patented it in England0 1ho patented it in the U.S.0 Research the contributions of Charles 1heatstone, Joseph "enry, and Samuel Morse. "ow did each of these men deal with issues of fame, wealth, and credit to other people ideas0 1hat effects have patents and copyrights had on modern technology0