9P.2.3.2 Electricity & Magnetism
Explain why currents flow when free charges are placed in an electric field, and how that forms the basis for electric circuits.
Explain and calculate the relationship of current, voltage, resistance and power in series and parallel circuits.
For example: Determine the voltage between two points in a series circuit with two resistors.
Describe how moving electric charges produce magnetic forces and moving magnets produce electric forces.
Use the interplay of electric and magnetic forces to explain how motors, generators, and transformers work.
Overview
MN Standard in Lay Terms
Charged particles experience an electric force when placed in an electric field. This electric field may extend through space and be supplied by other nearby point charges, a charged surface, or may be applied in a conductor such as a wire by a battery or other device. This force causes the charges to move and form an electric current. The kinetic energy transferred to charged particles from this interaction can transfer to other energy types in the electrical circuit in the forms of heat, light, other wave energies in the electromagnetic spectrum, sound, mechanical motion or to the storage of electrical potential energy in capacitors or to chemical potential energy stored in batteries.
Moving electric charges generate a magnetic field as evidenced by the deflection of a compass needle near a current carrying wire or by the action of an electromagnet. Likewise charges at rest in a wire or electric circuit can be induced to move when a magnetic field is moved relative to or changed near the wire or circuit forming a potential difference or electrical current. Clever arrangements of moving loops of wire in externally applied magnetic fields form the basis for electrical current generators. Clever arrangements of current carrying wires with the magnetic fields they generate, and externally applied magnetic fields, form the basis for electric motors.
Big Idea
9P.2.3.2.1
Net distributions or separations of electrical charge may be placed on or produced in insulators and conductors by a variety of methods. A distribution of electrical charge creates the conditions necessary to place forces on charges in conductors resulting the electrical current found in electrical circuits.
When positive charges are placed in an electric field the electric force acts to move the charges in the direction of the field, when negative charges are placed in an electric field the electric force acts to move the charges in a direction opposite the field direction.
As charges are displaced in an electric field work is done on them imparting kinetic energy to the charges giving them a drift velocity in conductors. This is the basis for electrical current flow.
When charges flow in conductors they transfer some of their kinetic energy to the resistance in the circuit which manifests itself in the form of heat energy. This transfer of energy is the basis for understanding the nature of energy "loss" due to electrical resistance in conductors.
9P.2.3.2.2
When a difference in Electrical Potential exists across an electrical circuit electrical energy can be transferred to the motion of charges resulting in the flow of electrical current. As this energy is added to the system energy is also transferred out by collisions in resistive materials in the form of heat. Resistance decreases the ability of charges to flow freely in a circuit thereby reducing the current flow. The current can be expressed as the ratio of the ability to impart energy to charges (potential difference measured in volts) to the ability to restrict the flow (electrical resistance measured in ohms) in Ohm's law as I=V/R. Ohm's Law, the conservation of energy, and methods of circuit analysis may be used to analyze series and parallel circuits of resistors for values of voltage, current, resistance and power.
Voltage or Potential Difference is the ability to impart energy to charge in a circuit (+) or take energy away (-) from charge in a circuit.
Electrical resistance transfers restricts the flow of charges and transfers energy out of an electrical circuit in the form of heat.
Electrical Current can be calculated from Ohm's Law I=V/R in Simple Circuits.
Electrical Power can be calculated from P=IV=I2R=V2/R
Electrical resistors in series increase the resistance in a circuit decreasing the overall electrical current.
Electrical resistors in parallel reduce the overall resistance of a circuit and actually allow more current to flow in the circuit because of the increased pathways.
Parallel circuits are used in homes because all devices have the same potential difference across them and draw needed power without affecting other devices in the circuit.
9P.2.3.2.3
When electrical charges move in free space or in a wire are they generate an associated magnetic field. Likewise when a magnetic field is "moved " near a charge it applies a force to the charge causing the charge to move.
Moving electric charges generate magnetic fields. These fields can be exploited in various ways including being used to make powerful electromagnets, meters, transformers, and recording devices.
Moving magnetic fields can place forces on charges causing them to separate in a wire creating a potential difference or cause an electrical current to flow in a closed circuit.
9P.2.3.2.4
Force interactions between moving charges and magnetic fields or between moving magnetic fields and stationary charges form the basis for conversion of mechanical energy to electrical energy and form electrical energy to mechanical energy.
Electrical generators rely on using other forms of energy to move magnetic fields relative to loops of wires to produce electrical current and potential.
Electrical motors rely on the electrical energy in the form of moving charges to generate magnetic fields that can interact with other magnetic fields to push the motor around converting the energy to mechanical energy.
Transformers rely on time varying electrical currents in a loop of wire to create a time varying magnetic field which is directed through another loop of wire. This varying field induces current and potential in this secondary loop in inversely varying proportion.
MN Standard Benchmarks
9P.2.3.2.1 Explain why currents flow when free charges are placed in an electric field, and how that forms the basis for electric circuits.
9P.2.3.2.2 Explain and calculate the relationship of current, voltage, resistance and power in series and parallel circuits. For example: Determine the voltage between two points in a series circuit with two resistors.
9P.2.3.2.3 Describe how moving electric charges produce magnetic forces and moving magnets produce electric forces.
9P.2.3.2.4 Use the interplay of electric and magnetic forces to explain how motors, generators, and transformers work.
The Essentials
xkcd.com Creative Commons License 2.5
Image URL (for hotlinking/embedding)
Forces due to fundamental interactions underlie all matter, structures and transformations; balance or imbalance of forces determines stability and change within all systems.
(Interactions, Stability, and Change)
What happens when matter interacts or changes and how do we characterize, explain, and predict what will happen immediately and over time? Interactions affect the structure, properties and behavior of matter. Interactions result in forces that may induce change or maintain stability in systems. All known physical phenomena can be explained by only a few types of interactions: gravitational, electromagnetic, and, at the nuclear scale, strong and weak interactions. These interactions are the source of forces between particles and particle decays. Unbalanced forces cause change in motion; balanced forces lead to stability, that is, to no change. Interactions may induce transformations of matter. When a transformation occurs, some things in a system change while others stay the same. Different factors affect the rate of different transformations. (Transformations here include both physical and chemical changes.)
Transfers of energy within and between systems never change the total amount of energy, but energy tends to become more dispersed; energy availability regulates what can occur in any process. (Energy and its Transformations)
All processes involve transfers of energy within and between systems. The concept of energy is useful because the total energy never changes and its availability limits what can occur in every interaction. At the macroscale, energy can be accounted for in many different forms. At the atomic scale, all forms of energy can be described in terms of kinetic energy, radiation, and energy that can be released or absorbed due to changes in the state of a system of interacting particles. All forms of energy can be quantified. Energy can be transferred from one system to another and transformed from one form to another, but it cannot be created or destroyed. In everyday language we speak of producing, using or wasting energy. This is because energy that is in concentrated form is useful for running machines, generating electricity for heat and light etc., while dissipated energy in the environment is not readily recaptured. Most processes tend to dissipate energy. Food, fuel and electric power are concentrated energy resources that can be moved from place to place to provide energy where needed. Food and fuel contain carbohydrates. These substances react with oxygen in burning or digestive processes to release thermal energy and carbon dioxide and other by-products. This process is a key energy provider for most animal life and for many forms of electrical generation, transportation and industrial machines.
Forces between two objects indicate that there is energy stored between them due to some interaction (e.g. gravitational, electromagnetic). Forces between two interacting objects are always in a direction such that motion in that direction would reduce the energy in the force field between them, but prior motion and other forces affect the actual direction of motion.
AAAS Benchmarks of Science Literacy and Atlas:
from Benchmarks Online - Project 2061 - AAAS (Physical Setting)
Energy Transformations (4E):
4E/H7 - Electrical potential energy is associated with the separation of mutually attracting or repelling charges.
4E/H9 - Many forms of energy can be considered to be either kinetic energy, which is the energy of motion, or potential energy, which depends on the separation between mutually attracting or repelling objects.
4E/H10 - If no energy is transferred into or out of a system, the total energy of all the different forms in the system will not change, no matter what gradual or violent changes actually occur within the system.
Motion (4F):
4F/H3a - When electrically charged objects undergo a change in motion, they produce electromagnetic waves around them.
Forces of Nature (4G):
4G/H2a - Electric forces acting within and between atoms are vastly stronger than the gravitational forces acting between the atoms. At larger scales, gravitational forces accumulate to produce a large and noticeable effect, whereas electric forces tend to cancel each other out.
4G/H2b - At the atomic level, electric forces between electrons and protons in atoms hold molecules together and thus are involved in all chemical reactions.
4G/H2c - Electric forces hold solid and liquid materials together and act between objects when they are in contact-as in sticking or sliding friction.
4G/H3 - Most materials have equal numbers of protons and electrons and are therefore electrically neutral. In most cases, a material acquires a negative charge by gaining electrons and acquires a positive charge by losing electrons. Even a tiny imbalance in the number of protons and electrons in an object can produce noticeable electric forces on other objects.
4G/H4ab - In many conducting materials, such as metals, some of the electrons are not firmly held by the nuclei of the atoms that make up the material. In these materials, applied electric forces can cause the electrons to move through the material, producing an electric current. In insulating materials, such as glass, the electrons are held more firmly, making it nearly impossible to produce an electric current in those materials.
4G/H4c - At very low temperatures, some materials become superconductors and offer no resistance to the flow of electrons.
4G/H4d - Semiconducting materials differ greatly in how well they conduct electrons, depending on the exact composition of the material.
4G/H5ab - Magnetic forces are very closely related to electric forces and are thought of as different aspects of a single electromagnetic force. Moving electrically charged objects produces magnetic forces and moving magnets produces electric forces.
4G/H5c - The interplay of electric and magnetic forces is the basis for many modern technologies, including electric motors, generators, and devices that produce or receive electromagnetic waves.
4G/H7 - Electric currents in the earth's interior give the earth an extensive magnetic field, which we detect from the orientation of compass needles.
4G/H8 - The motion of electrons is far more affected by electrical forces than protons are because electrons are much less massive and are outside of the nucleus.
Common Core Standards
Math Standards
(8.1.1.5) Express approximations of very large and very small numbers using scientific notation; understand how calculators display numbers in scientific notation. Multiply and divide numbers expressed in scientific notation, express the answer in scientific notation, using the correct number of significant digits when physical measurements are involved.
For example: (4.2×104)×(8.25×103) =3.465×108 , but if these numbers represent physical measurements, the answer should be expressed as 3.5×108 because the first factor, 4.2×104 , only has two significant digits.
(9.2.1.4) Obtain information and draw conclusions from graphs of functions and other relations.
Students can plot data of current and voltage to determine the resistance of a circuit.
(9.2.2.1) Represent and solve problems in various contexts using linear and quadratic functions.
(9.2.2.3) Sketch graphs of linear, quadratic and exponential functions, and translate between graphs, tables and symbolic representations. Know how to use graphing technology to graph these functions.
(9.3.1.3) Understand that quantities associated with physical measurements must be assigned units; apply such units correctly in expressions, equations and problem solutions that involve measurements; and convert between measurement systems.
For example: 60 miles/hour = 60 miles/hour × 5280 feet/mile × 1 hour/3600 seconds = 88 feet/second.
(9.3.1.5) Make reasonable estimates and judgments about the accuracy of values resulting from calculations involving measurements.
For example: Suppose the sides of a rectangle are measured to the nearest tenth of a centimeter at 2.6 cm and 9.8 cm. Because of measurement errors, the width could be as small as 2.55 cm or as large as 2.65 cm, with similar errors for the height. These errors affect calculations. For instance, the actual area of the rectangle could be smaller than 25 cm2 or larger than 26 cm2, even though 2.6 × 9.8 = 25.48.
(9.4.1.3) Use scatterplots to analyze patterns and describe relationships between two variables. Using technology, determine regression lines (line of best fit) and correlation coefficients; use regression lines to make predictions and correlation coefficients to assess the reliability of those predictions.
(9.4.2.3) Design simple experiments and explain the impact of sampling methods, bias and the phrasing of questions asked during data collection.
2010 Minnesota Academic Standards - English Language Arts K-12
Curriculum and Assessment Alignment Form
Grades 11-12 Literacy in Science and Technical Subjects
Minnesota Academic Standards: Language Arts
Anchor Standard | Benchmark |
1. Read closely to determine what the text says explicitly and to make logical inferences from it; cite specific textual evidence when writing or speaking to support conclusions drawn from the text. | 1. Cite specific textual evidence to support analysis of science and technical texts, attending to important distinctions the author makes and to any gaps or inconsistencies in the account. |
2. Determine central ideas or themes of a text and analyze their development; summarize the key supporting details and ideas. | 2. Determine the central ideas or conclusions of a text; summarize complex concepts, processes, or information presented in a text by paraphrasing them in simpler but still accurate terms. |
3. Analyze how and why individuals, events, and ideas develop and interact over the course of a text. | 3. Follow precisely a complex multistep procedure when carrying out experiments, designing solutions, taking measurements, or performing technical tasks; analyze the specific results based on explanations in the text. |
4. Interpret words and phrases as they are used in a text, including determining technical, connotative, and figurative meanings, and analyze how specific word choices shape meaning or tone. | 4. Determine the meaning of symbols, equations, graphical representations, tabular representations, key terms, and other domain-specific words and phrases as they are used in a specific scientific or technical context relevant to grades 11-12 texts and topics. |
5. Analyze the structure of texts, including how specific sentences, paragraphs, and larger portions of the text (e.g., a section, chapter, scene, or stanza) relate to each other and the whole. | 5. Analyze how the text structures information or ideas into categories or hierarchies, demonstrating understanding of the information or ideas. |
6. Assess how point of view or purpose shapes the content and style of a text. | 6. Analyze the author's purpose in describing phenomena, providing an explanation, describing a procedure, or discussing/reporting an experiment in a text, identifying important issues and questions that remain unresolved. |
7. Integrate and evaluate content presented in diverse media and formats, including visually and quantitatively, as well as in words. | 7. Integrate and evaluate multiple sources of information presented in diverse formats and media (e.g., quantitative data, video, multimedia) in order to address a question or solve a problem. |
8. Delineate and evaluate the argument and specific claims in a text, including the validity of the reasoning as well as the relevance and sufficiency of the evidence. | 8. Evaluate the hypotheses, data, analysis, and conclusions in a science or technical text, verifying the data when possible and corroborating or challenging conclusions with other sources of information. |
9. Analyze how two or more texts address similar themes or topics in order to build knowledge or to compare the approaches the authors take. | 9. Synthesize information from a range of sources (e.g., texts, experiments, simulations) into a coherent understanding of a process, phenomenon, or concept, resolving conflicting information when possible. |
10. Read and comprehend complex literary and informational texts independently and proficiently. | 10. By the end of grade 12, read and comprehend science/technical texts in the grades 11-12 text complexity band independently and proficiently. |
Misconceptions
The following misconceptions are taken from (Heller, P, & Stewart, G. (2010). College Ready Physics Standards: A Look to the Future. retrieved on 01/01/2011 from this site.
Several researched based sources for these misconceptions are found in that work.
1. "Electricity" is a vague term that refers to both whatever flows in a circuit (e.g., electric current, electrons) and to the flow of energy in a circuit. (9P.2.3.2.1)
a. 2. Electric current is the flow of energy, which is "used up" by the electrical device: (9P.2.3.2.1)
b. Current flows out of both terminals of a battery (or both connections in an electrical outlet) and meets at the electrical device, producing light and heat. Current flows from a battery (or other source of electricity) to a light bulb (or other item that consumes electricity), but not from the light bulb to the battery.
c. Current flows around a complete circuit, but objects like light bulbs use it up, so less current returns than leaves the source of the electricity.
3. Alternative Model of a Circuit (9P.2.3.2.1)
a. All of the electrical current (or electrons that make up the current) comes from (or is contained in) the battery or generator.
b. Wires are hollow like a water hose, and electric current (or electrons) move inside the hollow space.
c. The electric current (or electrons) from a battery is always the same, regardless of the number of electrical devices that are in a single loop (in series) or the number of loops connected to the battery (because how can the battery know what is hanging on it).
4. Electric current as the flow of electrons: (9P.2.3.2.2)
a. Electrons in wires jump from atom to atom during a current.
b. The flowing electrons carry energy to the electric device(s), deposit the energy in the devices, and then flow back to the battery.
c. The flowing electrons inside of wires move at the speed of light.
5. Resistors (9P.2.3.2.2)
a. Resistors consume charge.
b. Charges slow down as they go through a resistor.
6. Potential Difference ("voltage") (9P.2.3.2.1)
a. Current is the same thing as voltage. Voltage flows through a circuit.
b. Voltage is energy.
c. The bigger the battery, the more voltage.
7. Power and energy are the same thing. (9P.2.3.2.1,(9P.2.3.2.2)
8. "Voltage" (9P.2.3.2.1)
a. There is no connection between "voltage" and electric field.
b. Voltage is energy
9. Connection Between Current Electricity and Magnetism (9P.2.3.2.3)
a. Charges, when released, will move toward the poles of a magnet.
b. North and south magnetic poles are the same as positive and negative charges.
c. Magnetic poles can be isolated.
d. A suspended battery (2-ended) will align in the north-south direction like a magnet.
10. Only magnets produce magnetic fields (forces).(9P.2.3.2.3)
11. Only charges can produce electric fields (forces). (9P.2.3.2.3)
12. Generating Electricity (9P.2.3.2.4)
a. When generating electricity only the magnet can move.
b. Generating electricity requires no work.
c. A magnetic field, rather than a changing magnetic field, causes an electric current.
13. Charges at rest can experience magnetic forces. (9P.2.3.2.3)
14. Field lines are real. Field lines can begin/end anywhere. There are a finite number of field lines. If a charge or compass is not on a field line, it feels no force. (9P.2.3.2.1)
15. Fields don't exist unless there is something to detect them. (9P.2.3.2.1 )
16. Forces at a point exist without a compass, mass, or charge there. (9P.2.3.2.1)
17. A field and a force are the same thing and in the same direction. (9P.2.3.2.1)
18. Magnetic fields are the same as electric fields.(9P.2.3.2.3)
Vignette
A Conceptual Introduction to Electric Circuits and Ohm's Law
Ms. Watt wants to introduce electric circuits and Ohm's Law to her students. Prior to this lesson, she had students investigate how to light miniature flashlight bulbs with a D battery and some wire. From that investigation students understand that current travels in a closed circuit from one end of the battery to the other, and that a light bulb will light if the current travels through the filament.
To introduce the lesson, Ms. Watt shows the two diagrams below, and has the students consider a discussion about the diagram between two students:
Figure 1 Figure 2
Student 1: "I think the current will have to be greater in the first diagram in order to light the two light bulbs. The light bulb in figure two doesn't need as much current."
Student 2: "I think there will be more current in the second diagram because there is less resistance to effect the current."
Students discuss the conversion between the two students in groups of 3 or 4. Ms. Watt uses a student response system (clickers) to get the students to vote on which statement they believe to be correct. After looking at the class votes with the class, she has the students build the circuits using two miniature light bulbs, a D size battery, and wires. Students write down their observations of the light bulbs in each circuit and post their findings on 3 ft x 2 ft whiteboards. The students share their findings. Groups found that the circuit with the two light bulbs were less bright than the circuit with one light bulb. Ms. Watt posses the question "Why did the circuit with two light bulbs have less brightness than the circuit with one light bulb?"
Ms. Watt has the students go to the PhET website (www.phet.colorado.edu) to use the Circuit Construction Kit (DC) simulation to answer this question. Students build both circuits and watch the current flow through each circuit. They observe that the electrons flow quicker through the wire in the one light bulb circuit compared to the two light bulb circuit. After students have made this observation, Ms. Watt shows the students how to use the simulation ammeter. She asks the students to make a graph of the number of light bulbs (in series) verses the current reading on the ammeter.
This lesson leads into her next day's lesson about Ohm's Law, where Ms. Watt will have the students return to Circuit Construction Kit (DC) simulation to investigate the relationship between current, the number of batteries (voltage), and the number of light bulbs (resistance).
Resources
Instructional suggestions/options
Modeling Physics Resources in Electricity and Magnetism at Arizona State University
Suggested Labs and Activities
Investigating mutual inductance with simple transformers.
Create or have students create a set of small transformers in this manner. Wrap 50 to 75 turns of insulated wire on a large nail. The turns may be held in place by thin tape or some adhesive. Wrap 10-20 turns of a second wire on the top of this wire. Connect a voltmeter to the 50-75 turn coil. Momentarily connect and disconnect the dry cell and have the students write down the maximum voltage reading they get. Repeat this a couple of times. Now connect the voltmeter to the 10-20 turn coil and momentarily connect and disconnect the dry cell to the 50-75 turn coil writing down the maximum voltage. Repeat the same experiment this time using a milli-ampmeter to measure current. Have the students summarize their findings. Finish up with a discussion about how transformers work and show some everyday ac to dc converters with their transformers exposed.
Demonstrate the deflection of moving charges due to a magnetic field with a CRT or old black and white T.V. (Do not do this with a color computer monitor or color T.V. that you still plan to use for its original purpose!)
(Use photo at will it is mine, Mike Maas)
Vernier Investigations:
Vernier technology is a source of data collection that allows students to accurately predict and analysis data. The links below are the complete labs as posted by Vernier Software and Technology.
(9P.2.3.2.1) Electrical Energy - Determine the electrical energy used by the motor and compare it to the change in gravitational potential energy of the mass.
(9P.2.3.2.2) Ohm's Law - Determine the mathematical relationship between current, potential difference, and resistance in a simple circuit.
(9P.2.3.2.2) Series and Parallel Circuits - To study current flow and voltages in series and parallel circuits. Use Ohm's law to calculate equivalent resistance of series and parallel circuits.
(9P.2.3.2.1) Capacitors - Measure an experimental time constant of a resistor-capacitor circuit. Compare the time constant to the value predicted from the component values of the resistance and capacitance. Measure the potential across a capacitor as a function of time as it discharges and as it charges. Fit an exponential function to the data. One of the fit parameters corresponds to an experimental time constant.
(9P.2.3.2.3) The Magnetic Field in a Coil - Determine the relationship between magnetic field and the number of turns in a coil. Determine the relationship between magnetic field and the current in a coil.
(9P.2.3.2.3) The Magnetic Field in a Slinky - Determine the relationship between magnetic field and the current in a solenoid. Determine the relationship between magnetic field and the number of turns per meter in a solenoid. Study how the field varies inside and outside a solenoid. Determine the value of μ0, the permeability constant.
(9P.2.3.2.3) The Magnetic Field of a Permanent Magnet - Compare the distance dependence of the magnetic field to the magnetic dipole model. Measure the magnetic moment of a magnet.
Coulomb's Law for Two Charged Spheres (9P.2.3.2.1) - Explore the inverse square law proposed by Coulomb use Video Analysis.
Using the Coulomb Force Law to Determine Discharge Rate (9P.2.3.2.1) - Use the laws of mechanics and Coulomb's Law to find out how much charge is on two charged balls.
Electric Field Due to a Line of Charge (9P.2.3.2.1) - Examine a charged rod exerting a force on a hanging "test charge" and determine if a theoretical equation that describes the relationship between r, L and the measured electric field hold true.
Resistance and Ohm's Law (9P.2.3.2.2) - Compare the behavior of a flashlight bulb to that of a carbon resistor and determine whether or not these devices obey Ohm's Law.
Using RC Decay to Determine a Capacitance (9P.2.3.2.1) - Use video analysis to determine a capacitance using RC Decay.
Exploring Faraday's Law (9P.2.3.2.3) - Interpret Faraday's Law to explain why Emf varies when a rod shaped magnet is moved back and forth through a coil of wire.
PASCO "Physics with the Xplorer GLX"
Activity 22 - Ohm's Law: Current, Voltage, Resistance (9P.2.3.2.1) (9P.2.3.2.2)
PDF (592 KB) Measure the voltage across a resistor and the current through the resistor as the voltage is changed. Confirm the relationship of the current to voltage for a fixed resistance.
Activity 23A - Voltage in a Series Circuit (9P.2.3.2.2)
PDF (1 MB) Determine the relationship between voltage and the number of light bulbs that are connected to a voltage source in a series circuit.
Activity 23B - Voltage in a Parallel Circuit (9P.2.3.2.2)
PDF (928 KB) Determine the relationship between voltage and the number of light bulbs that are connected to a voltage source in a parallel circuit.
Activity 24A - Current in a Series Circuit (9P.2.3.2.2)
PDF (1.8 MB) Determine the relationship between current and the number of light bulbs that are connected to a voltage source in a series circuit.
Activity 24B - Current in a Parallel Circuit (9P.2.3.2.2)
PDF (1.8 MB) Determine the relationship between current and the number of light bulbs that are connected to a voltage source in a parallel circuit.
Activity 26 - Electromagnetic Induction-Magnet and Coil (9P.2.3.2.3)
PDF (1.3 MB) Measure the voltage across a coil of wire when a bar magnet moves through the coil or wire. Compare the voltage to the number of turns of wire in the coil.
Student Practicum Problems:
Practicums For Physics Teachers (Ryan, Henry and Barber, Jon, 2008)
Two high school teachers developed practicums for students to solve problems using an understanding of physics concepts and critical thinking skills. The link below does not get you to the activity, only an order form for the book. This is the only way of purchasing these practicums. See this page.
Resistivity (p. 88) (9P.2.3.2.1) - Determine the length of Nichrome wire needed to have a resistance of 2 ohms. Then predict the amperage in a circuit containing the Nichrome wire, ammeter, a voltmeter with the power source set at 6.0 volts.
Blow the Circuit (p. 91) (9P.2.3.2.1) - Prepare a parallel circuit with one .85 amp fuse so that when the circuit is initially activated it has one light bulb left out of it's receptacle and all other bulbs lit. Then when the last bulb is turned into its receptacle the fuse blows and all the lights go out except one.
Resistance Will Vary (p. 93) (9P.2.3.2.2) - Determine the amount of resistance needed for two devices in a parallel circuit to provide the proper current and voltage for each device and set the variable resistors accordingly.
Resistance is Futile (p. 95) (9P.2.3.2.2) - Determine the resistance of a hidden resistor in a circuit and the potential difference across one resistor in a parallel branch.
Additional resources
The Physics Classroom: Resource for both teachers and students. Website is sectioned into Read/Watch/Interact, Practice/Review, and Teacher Tools.
123Physics: Regents Review Questions, Physics Lessons, Videos, and Physics Clipart
Falstad.com: simulation applets on electric and magnetic fields, and links to other simulations.
ComPADRE is filling a stewardship role within the National Science Digital Library for the educational resources used by broad communities in physics and astronomy. This partnership of the American Association of Physics Teachers (AAPT), the American Astronomical Society (AAS), the American Institute of Physics/Society of Physics Students (AIP/SPS), and the American Physical Society (APS) helps teachers and learners find, and use, high quality resources through collections and services tailored to their specific needs.
The Physics Front
The Physics Front provides high quality resources for the teaching of physics and physical sciences courses. You may search or browse the Physics Front in order to find materials appropriate for your physics classes. Additionally, registering will allow you to share your experiences using materials. The Physics Front is a free service provided by the American Association of Physics Teachers in partnership with the NSF/NSDL. See this page.
Physics Win or Physics Fail?
Use your knowledge of physics to put these videos to the test!
Inspired by Rhett Allain's physics explanations at Dot Physics, Dan Meyer's blog series "What Can You Do With This?", and Dan's TEDx plea for a math curriculum makeover, I have been collecting video clips that are prime for my physics students to analyze.
Videos are categorized by topic to help teachers locate videos for the concepts at hand. Several videos are listed under multiple topics. The videos are presented without any further questions other than "Physics win or physics fail?" (real or fake?) See this page.
Pretty Good Physics
If you are looking around for some good labs to use or to tweek, check this site out. Items have been put here for physics teachers, by physics teachers, and range from first-year high school physics to AP material. The emphasis is on labs, but explanatory material is also available. The University sources on the bottom will direct you to even more great material. The collection of materials is growing all of the time.
Vocabulary/Glossary
Electron: A negatively charged particle that orbits the nucleus of the atom.
Proton: A positively charged particle that, along with the neutron, occupies the nucleus of the atom.
Coulomb: The SI unit measure of electrical charge. The smallest unit of charge is e=1.602 x 10-19 C
Conductor: A material that allows electrical charge to flow freely.
Insulator: A material that does not allow for the free flow of electrical charge.
Conduction: Transfer of electrical charge through a conductor.
Induction: Forced separation of electrical charge due to electric forces and fields.
Coulombs Law: The expression of electrical force expressing the forces direct proportionality as being proportional to each quantity of charge and inversely proportional to the square of the distance between them.
Electric Field: The electric field is a vector field with SI units of newtons per coulomb (N/C) or, equivalently, volts per meter (V/m). The strength or magnitude of the field at a given point is defined as the force that would be exerted on a small positive test charge placed at that point; the direction of the field is given by the direction of that force.
Electrical Potential: The ability of an electric field to transfer energy to a quantity of charge, measured in volts. 1 volt has the ability to transfer 1 joule of energy to 1 coulomb of charge.
Electrical Current: The flow of electrical charge through a given cross sectional area, measured in amps. 1 amp = 1 coulomb of charge passing in 1 second.
Resistance: The flow of electrical charge is impeded by its interactions in a material resulting in a energy transfer to heating, measured in Ohm's.
Ohm's Law: The relationship between electrical potential, the flow of electrical current, and electrical resistance in a simple circuit. V=IR
Series Circuit: A circuit in which all elements have only one point in common so that the electrical current through each is the same and the overall resistance is the result of the addition of each resitive element.
Parallel Circuit: A circuit in which all elements have two points in common and the overall current in the circuit is the sum of the currents in all branches.
Motor: A device which converts electromagnetic energy to mechanical energy via the electromagnetic interaction.
Generator: A device that converts mechanical energy to electromagnetic energy via the electromagnetic interaction.
Transformer: A device which can step up or step down AC voltages and current via the electromagnetic interaction.
Web Based Simulations
University of Colorado PhET Simulations
Each of the following visually appealing and engaging simulations allow students to experience and experiment with various configurations of Electricity and Magnetism as a powerful supplement to real world experimentation. Students may interact with and vary the physical parameters of the simulations. Many of the simulations allow students to visualize and engage with phenomena that cannot be done in the high school lab setting. All of these simulations have accompanying lesson plans, student documents, and teacher resources developed by teachers for you to use in your classroom.
Balloons and Static Electricity
(9P.2.3.2.1)
Why does a balloon stick to your sweater? Rub a balloon on a sweater, then let go of the balloon and it flies over and sticks to the sweater. View the charges in the sweater, balloons, and the wall.
(9P.2.3.2.1)
Move point charges around on the playing field and then view the electric field, voltages, equipotential lines, and more. It's colorful, it's dynamic, it's free.
(9P.2.3.2.1)
Add charges to the Field of Dreams and see how they react to the electric field. Turn on a background electric field and adjust the direction and magnitude.
(9P.2.3.2.1)
Play hockey with electric charges. Place charges on the ice, then hit start to try to get the puck in the goal. View the electric field. Trace the puck's motion. Make the game harder by placing walls in front of the goal. This is a clone of the popular simulation of the same name marketed by Physics Academic Software and written by Prof. Ruth Chabay of the Dept of Physics at North Carolina State University.
(9P.2.3.2.1)
Look inside a resistor to see how it works. Increase the battery voltage to make more electrons flow though the resistor. Increase the resistance to block the flow of electrons. Watch the current and resistor temperature change.
(9P.2.3.2.2)
See how the equation form of Ohm's law relates to a simple circuit. Adjust the voltage and resistance, and see the current change according to Ohm's law.
Circuit Construction Kit (DC Only)
(9P.2.3.2.2)
An electronics kit in your computer! Build circuits with resistors, light bulbs, batteries, and switches. Take measurements with the realistic ammeter and voltmeter. View the circuit as a schematic diagram, or switch to a life-like view.
Circuit Construction Kit (AC and DC) (9P.2.3.2.2)
This new version of the CCK adds capacitors, inductors and AC voltage sources to your toolbox! Now you can graph the current and voltage as a function of time.
(9P.2.3.2.3)
Ever wonder how a compass worked to point you to the Arctic? Explore the interactions between a compass and bar magnet, and then add the earth and find the surprising answer! Vary the magnet's strength, and see how things change both inside and outside. Use the field meter to measure how the magnetic field changes.
(9P.2.3.2.3) (9P.2.3.2.4)
Play with a bar magnet and coils to learn about Faraday's law. Move a bar magnet near one or two coils to make a light bulb glow. View the magnetic field lines. A meter shows the direction and magnitude of the current. View the magnetic field lines or use a meter to show the direction and magnitude of the current. You can also play with electromagnets, generators and transformers!
(9P.2.3.2.3)
Light a light bulb by waving a magnet. This demonstration of Faraday's Law shows you how to reduce your power bill at the expense of your grocery bill.
(9P.2.3.2.3)
Explore the interactions between a compass and bar magnet. Discover how you can use a battery and wire to make a magnet! Can you make it a stronger magnet? Can you make the magnetic field reverse?
Generator (9P.2.3.2.4)
Generate electricity with a bar magnet! Discover the physics behind the phenomena by exploring magnets and how you can use them to make a bulb light.
Web Based Instructional Videos:
An oldie but a goodie, regarded as a classic on electrostatics
Coulombs Law by Eric Rogers
Here, manic Princeton professor Eric Rogers hosts, continually removing and replacing his eyeglasses, ordering around lab assistants --- he forcefully breaks a glass test tube in the hands of an assistant to demonstrate the inelasticity of water --- and furiously pounds equations on a blackboard (Leacock says the scribblings must have lasted 45 minutes, in what must be one of the more necessary cuts in the history of educational film.) Rogers finally conducts an experiment with a student, placing them in a metal cage, which he then charges with electricity, demonstrating through the inverse square law that his assistant (Leacock's trusting daughter Elspeth) is not harmed by the charge.
The following Videos are from the Annenburg Foundation's Mechanical Universe Collection Video on Demand
This series helps teachers demystify physics by showing students what it looks like. Field trips to hot-air balloon events, symphony concerts, bicycle shops, and other locales make complex concepts more accessible. Inventive computer graphics illustrate abstract concepts such as time, force, and capacitance, while historical reenactments of the studies of Newton, Leibniz, Maxwell, and others trace the evolution of theories. The Mechanical Universe helps meet different students' needs, from the basic requirements of liberal arts students to the rigorous demands of science and engineering majors. This series is also valuable for teacher professional development. See this page.
28. Static Electricity (9P.2.3.2.1)
Eighteenth-century electricians knew how to spark the interest of an audience with the principles of static electricity.
29. The Electric Field (9P.2.3.2.1)
Faraday's vision of lines of constant force in space laid the foundation for the modern force field theory.
30. Potential and Capacitance (9P.2.3.2.1)
Franklin proposes a successful theory of the Leyden jar and invents the parallel plate capacitor.
31. Voltage, Energy, and Force (9P.2.3.2.1)
When is electricity dangerous or benign, spectacular or useful?
32. The Electric Battery (9P.2.3.2.1)
Volta invents the electric battery using the internal properties of different metals.
33. Electric Circuits (9P.2.3.2.2)
The work of Wheatstone, Ohm, and Kirchhoff leads to the design and analysis of how current flows.
34. Magnetism (9P.2.3.2.3)
Gilbert discovered that the earth behaves like a giant magnet. Modern scientists have learned even more.
35. The Magnetic Field (9P.2.3.2.3)
The law of Biot and Sarvart, the force between electric currents, and Ampère's law.
37. Electromagnetic Induction (9P.2.3.2.4)
The discovery of electromagnetic induction in 1831 creates an important technological breakthrough in the generation of electric power
38. Alternating Current (9P.2.3.2.4)
Electromagnetic induction makes it easy to generate alternating current while transformers make it practical to distribute it over long distances.
HippoCampus is a project of the Monterey Institute for Technology and Education (MITE). The goal of HippoCampus is to provide high-quality, multimedia content on general education subjects to high school and college students free of charge. This site could be used in conjuction with your course to help teach the standards at various levels.
Electric Charge and Coulomb Force (9P.2.3.2.1)
Electric Field and Electric Field Lines (9P.2.3.2.1)
Charges in Conductors (9P.2.3.2.1)
Electrical Circuits (9P.2.3.2.1,9P.2.3.2.2)
Magnetic Forces on Charges and Current Carrying Wires (9P.2.3.2.3,9P.2.3.2.4)
Win/Fail Physics!
Use your knowledge of physics to put these videos to the test!
Inspired by Rhett Allain's physics explanations at Dot Physics, Dan Meyer's blog series "What Can You Do With This?", and Dan's TEDx plea for a math curriculum makeover, I have been collecting video clips that are prime for my physics students to analyze.
Videos are categorized by topic to help teachers locate videos for the concepts at hand. Several videos are listed under multiple topics. The videos are presented without any further questions other than "Physics win or physics fail?" (real or fake?) See this page.
Assessment
Assessment of Students
Multiple Choice Review Questions with Answers and Learning Links for the Concepts
Peer Instruction: A User's Manual, (Mazur, Eric, Harvard University, Prentice Hall, 1997) - conceptual questions for using Student Response Systems.
Electrostatics
CT1: Static electricity (9P.2.3.2.1)
CT2: Static electricity (9P.2.3.2.1)
CT5: Forces between positive and negative charges (9P.2.3.2.1)
CT6: Electric fields (9P.2.3.2.1)
CT10: Electric potential (9P.2.3.2.1)
CT12: Electric potential and distance (9P.2.3.2.1)
DC Circuits
CT1: Combinations of resistors (9P.2.3.2.2)
CT2: Combinations of resistors (9P.2.3.2.2)
CT4: brightness of bulbs and shorted circuits (9P.2.3.2.2)
CT5: Bulbs connected in series and parallel (9P.2.3.2.2)
CT6: Bulbs connected in series and parallel (9P.2.3.2.2)
CT8: brightness of bulbs and shorted circuits (9P.2.3.2.2)
CT11: Combinations of resistors and current (9P.2.3.2.2)
Magnetism
CT3: moving charge in a magnetic field (9P.2.3.2.3)
CT4: Earth's magnetic field and moving charges (9P.2.3.2.3)
CT7: Force on a current in an magnetic field (9P.2.3.2.3)
CT8: Force on a current in an magnetic field (9P.2.3.2.3)
CT9: DC currents and transformers (9P.2.3.2.4)
CT10: DC currents and transformers (9P.2.3.2.4)
CT11: changing magnetic fields and induced currents (9P.2.3.2.4)
CT12: changing magnetic fields and induced currents (9P.2.3.2.4)
(9P.2.3.2.2) 1. One ohm is a unit of
a. current.
b. voltage.
c. electric charge.
d. resistance.
e. power.
Answer D
(9P.2.3.2.2) 2. Three different resistors: 10 ohm, 20 ohm, and 20 ohm are connected in series, the overall resistance is:
a. 5 ohms.
b. 10 ohms
c. 15 ohms
d. 20 ohms
e. 50 ohms
Answer E
(9P.2.3.2.2) 3. Three different resistors: 10 ohm, 20 ohm, and 20 ohm are connected in parallel, the overall resistance is:
a. 5 ohms.
b. 10 ohms
c. 15 ohms
d. 20 ohms
e. 50 ohms
Answer A
(9P.2.3.2.2) 4. A simple has a voltage of 5.0 V and a resistance of 1000 ohms. What is the current?
a. 1 mA
b. 5 mA
c. 10 mA
d. 25 mA
e. 1000 mA
Answer B
(9P.2.3.2.4) 5. What do you need to do with the magnet to get the lamp to light brightly?
a. Hold the magnet in the center of the coil
b. Hold the magnet as close as possible to the lamp itself?
c. Move the magnet up and down vertically slowly
d. Move the magnet left and right very quickly
e. By holding the magnet perpendicular to the wire coil.
(9P.2.3.2.4) 6. What would happen if electrical power were transmitted from a generating station at 120 Volts?
a. The cost of electricity would be cheaper.
b. All the power would be lost to joule heating
c. The cost of electricity would remain the same
d. All the power would be converted to electrical energy more efficiently
Answer B
(9P.2.3.2.1) 7. A basic property of electric charge is that
a. like charges attract.
b. unlike charges repel.
c. unlike charges attract.
d. like charges sometimes attract and sometimes repel.
Answer C
(9P.2.3.2.1) 8. A system consisting of an electron and a neutron has a net charge of
a. +1.6 x 10-19 C.
b. -1.6 x 10-19 C.
c. +3.2 x 10-19 C.
d. zero.
Answer D
(9P.2.3.2.2) 9. The unit for current is the
a. ohm.
b. ampere.
c. volt.
d. coulomb.
Answer B
(9P.2.3.2.1) 10. What is the initial net charge of the balloon?
a. positive
b. negative
c. neutral
d. it is impossible to know
Answer C
(9P.2.3.2.1) 11. What is the net charge of the balloon after it is rubbed on the sweater?
a. positive
b. negative
c. neutral
d. it is impossible to know
Answer B
(9P.2.3.2.1) 12. What is the net charge of the sweater after it is rubbed with the balloon?
a. positive
b. negative
c. neutral
d. it is impossible to know
Answer A
(9P.2.3.2.2) Questions 13 and 14: The figure at the top left shows a single light in series with a battery of 10 volts.
13. What is the resistance for the light bulb?
a. 0 ohm
b. 0.1 ohm
c. 1 ohm
d. 2 ohm
e. 10 ohm
Answer E
14. What would be the current if a second lamp is connected as shown in the right figure?
a. 0 amp
b. 0.5 amp
c. 1 amp
d. 2 amp
e. 10 amp
Answer B
The figure shows the path of the positive charge to reach the goal by two unknown charges A and B
(9P.2.3.2.1) 15. What is the sign of A?
a. positive
b. negative
c. both positive and negative
d. neutral
Answer A
(9P.2.3.2.1) 16. What is the sign of B?
a. positive
b. negative
c. both positive and negative
d. neutral
Answer B
Assessment of Teachers
Modeling Instruction in High School Physics, Chemistry, Physical Science, and Biology
Materials and readings for teacher discussion and use for professional development
The Modeling Method of High School Physics Instruction has been under development at Arizona State University since 1990 under the leadership of David Hestenes, Professor of Physics. The program cultivates physics teachers as school experts on effective use of guided inquiry in science teaching, thereby providing schools and school districts with a valuable resource for broader reform. Program goals are fully aligned with National Science Education Standards. The Modeling Method corrects many weaknesses of the traditional lecture-demonstration method, including fragmentation of knowledge, student passivity, and persistence of naive beliefs about the physical world. Unlike the traditional approach, in which students wade through an endless stream of seemingly unrelated topics, the Modeling Method organizes the course around a small number of scientific models, thus making the course coherent. In 2000 the program was extended to physical science and in 2005 to chemistry, by demand of committed teachers.
Peer Instruction: A User's Manual, (Mazur, Eric, Harvard University, Prentice Hall, 1997) - conceptual questions for using Student Response Systems.
Electrostatics
CT1: Static electricity (9P.2.3.2.1)
CT2: Static electricity (9P.2.3.2.1)
CT5: Forces between positive and negative charges (9P.2.3.2.1)
CT6: Electric fields (9P.2.3.2.1)
CT10: Electric potential (9P.2.3.2.1)
CT12: Electric potential and distance (9P.2.3.2.1)
DC Circuits
CT1: Combinations of resistors (9P.2.3.2.2)
CT2: Combinations of resistors (9P.2.3.2.2)
CT4: brightness of bulbs and shorted circuits (9P.2.3.2.2)
CT5: Bulbs connected in series and parallel (9P.2.3.2.2)
CT6: Bulbs connected in series and parallel (9P.2.3.2.2)
CT8: brightness of bulbs and shorted circuits (9P.2.3.2.2)
CT11: Combinations of resistors and current (9P.2.3.2.2)
Magnetism
CT3: moving charge in a magnetic field (9P.2.3.2.3)
CT4: Earth's magnetic field and moving charges (9P.2.3.2.3)
CT7: Force on a current in an magnetic field (9P.2.3.2.3)
CT8: Force on a current in an magnetic field (9P.2.3.2.3)
CT9: DC currents and transformers (9P.2.3.2.4)
CT10: DC currents and transformers (9P.2.3.2.4)
CT11: changing magnetic fields and induced currents (9P.2.3.2.4)
CT12: changing magnetic fields and induced currents (9P.2.3.2.4)
Differentiation
Strategies from The Inclusive Classroom: Teaching Mathematics and Science to English-Language Learners, (Jarrett, Denise, Northwest Regional Educational Laboratory, Nov. 1999)
Thematic Instruction: Theme-based units can help ELL students connect prior knowledge to language and real-world applications.
Cooperative Learning: Students use language related to task, while conversing and tutoring one another.
Inquiry and Problem Solving: Inquiry and problem solving can be used prior to proficiency in English. Inquiry approaches in science can help student's language acquisition as well as their content knowledge.
Vocabulary Development: Students learn the meaning of words best during investigations and activities, instead of as a vocabulary list.
Modify Speech: Teachers can help ELL students by using an active voice, limiting new terms, using visual support, and paraphrasing or repeating difficult concepts. Slowing down speech, speaking clearly, and using a simple language structure will help ELL students with understanding.
Make ELL Students Feel Welcome: Encourage ELL students to express ideas, thought, and experiences. Focus on what student is say, not how they say it.
Book: Science Education for Gifted Students: A Gifted Child Today Reader (Johnsen, S. K. and Kendrick, J., 2005, Prufrock Press, Inc.)
A substantial resource for SpEd, ELL with specific suggestions for science classrooms. Teaching Today | How-To Articles | Supporting Special Education Students in Science
Parents/Admin
Administrators
Ideas adapted from (Daniels, H, Hyde, A, Zemelman, S, & Heinmann, Initials. (2005). Best practice: Today's standards for teaching and learning in America's schools. Portsmouth,NH:)
1. Students being challenged in thinking how the electric charge and electric circuits (i.e. the relationship between current, resistance, and voltage in electric circuits.)
2. Students testing their understanding of electric charge and electric circuits with investigations or solving real life scenarios using the concepts and associated equations.
3. Students taking on responsibility for their own learning.
4. Students working in collaborative groups, analyzing, synthesizing, and defending conclusions.
5. Students sharing explanations for results of investigation and understanding of concepts.
6. Students continuously assessing and being assessed on their understanding of electric charge, electric circuits, and magnetism.
7. Students' concepts are being built on prior knowledge of motion, atomic structure, and forces.