Unit 3: Fundamental Forces, Electricity & Magnetism

Instructional Resources

OAS-S: PH.PS2.4^✝, PH.PS2.5, and PH.PS3.5

Bundled Standards Analysis: Fundamental Forces: Electricity & Magnetism

^✝Note: Focus is on electrostatic force (Coulomb’s Law) between charged particles. Newton’s Law of Universal Gravitation is addressed in the “Forces and Motion” bundle.

Driving Question

• How are force fields being used to improve human life?
  

Essential Questions

• How can we use Coulomb’s Law to make predictions about the forces objects will experience?

• How could a system be designed to determine if a relationship between electric current and magnetic fields exists?

• How does the energy of objects change and transfer while interacting in fields? 

Examples of Student-Developed Initial Questions

• How can we determine the forces acting on two nearby charges?

• How is electric current in a wire related to magnetism?

• Can a magnetic field affect an electric circuit?

• What are electric and magnetic fields?

• What can magnetic fields do to a charged particle or a current in a wire?  

Prior Knowledge

Each dimension in the Oklahoma Academic Standards for Science grows in complexity and sophistication across the grades. To learn more about the prior knowledge and skills students have developed in previous grades associated with the standards in this bundle, check out the links below.

Science and Engineering Practices 

Disciplinary Core Ideas 

Crosscutting Concepts 

Science and engineering practices (SEP) in Physics build on K-8 experiences. This bundle of standards engages students with the following SEPs: 

• Using Mathematics and Computational Thinking

• Planning and Carrying Out Investigations

• Developing and Using Models

Disciplinary core ideas (DCI) in Physics build on K-8 experiences. This bundle of standards explores the following areas:

• Types of Interactions

• Definitions of Energy

• Relationship Between Energy and Forces

Crosscutting concepts (CCC) in Physics build on K-8 experiences. This bundle of standards leverages the following ways of thinking about science ideas: 

• Patterns

• Cause and Effect

• Energy and Matter

Launch Task: Phenomena Ideas

Phenomena are observable events that occur in the universe and that we can use our science knowledge to explain or predict. Engineering involves designing solutions to problems that arise from phenomena and using explanations of phenomena to design solutions. Instructional sequences are more coherent when students investigate phenomena or design problems by engaging in science and engineering practices. Read this STEM Teaching Tool Brief #28 to learn more about the characteristics of a good phenomenon or design problem for anchoring student learning.

Each phenomenon below includes teacher information resources (e.g., information about the phenomenon, data resources, videos, simulations, etc.). Due to the length or accessibility of the content, teachers should screen the resources and pull sections, photos, quotes, and data that are appropriate for Physics students to ask questions, investigate, analyze, describe, evaluate, etc.

Phenomenon: Laser printers create copies of documents without using ink.

Laser printers use electrical charges to create copies of documents. Educators can assist students with investigating how laser printers work through text (e.g., “How Laser Printers Work”), and/or observations of a laser printer in action (in person or via videos such as “How a Laser Printer Works”). Students can develop models (e.g., drawings, diagrams) to illustrate the electrical forces involved in laser printers and how those forces interact to create images. Students can also use mathematical representations of Coulomb’s Law to describe and predict the electrostatic forces between the objects in a laser printer.

Phenomenon: Electric generators transfer kinetic energy from different sources to electrical energy through fields.

Two of the most visible symbols of electric energy generation in Oklahoma are wind turbines in the western half of the state and the hydroelectric dams that create the numerous lakes in the eastern half. Although these structures look different, they use the same physics principles to produce electrical energy. All electric generators use changing magnetic fields to transfer kinetic energy into electrical energy and produce electric currents, a principle called electromagnetic induction. Educators can provide students with resources for wind energy and hydroelectric plant locations to determine which of these facilities are in their region. Educators can provide resources that describe how wind turbines (e.g., Inside a Wind Turbine, Energy 101: Wind Turbines, Tour a Wind Turbine ) and hydroelectric plants (e.g., How a Hydropower Plant Works, Turbines in the Kolnbrein Dam) work to identify similarities and differences in the machines that produce electric power. Students can further explore this principle using simulations (e.g., Faraday's Law) or by building a simple generator (e.g., Energy Innovator).

Engagement Strategies 

• Educators can leverage the Student Actions and Teacher Actions found in the Fundamental Forces: Electricity and Magnetism bundled standards analysis for specific ways of engaging students with these science ideas.

• This example of a secondary science cycle of learning can support educators in developing coherent sequences of learning.
  

• A Driving Question Board can be used to encourage students to share their wonderings and guide teaching/learning throughout the unit. More strategies that support students with figuring out science ideas can be found within the Science Engagement Strategies section of the Framework. 

What It Looks Like in the Classroom

In science and engineering, evidence-based effective instruction focuses on students engaging in science and engineering investigations and design to explain phenomena or develop solutions to a problem. This section reflects a science cycle of learning that supports implementing the identified standards within this unit.

"What It Looks Like in the Classroom" is broken into Narrative Parts, written around the different Essential Questions listed at the top. Each Narrative Part includes examples for how to integrate the science and engineering practices, disciplinary core ideas, and crosscutting concepts for each standard, and includes examples of evidence teachers can gather from students that provides information about what they do and do not understand.

Narrative Part 1 of 2

Essential Question: How can we use Coulomb’s Law to make predictions about the forces objects will experience?

OAS-S:

PH.PS2.4 Use mathematical representations of Newton’s Law of Gravitation and Coulomb’s Law to describe and predict the gravitational and electrostatic forces between objects.

 3-Dimensional Narrative

Evidence of Understanding 

Provide students with opportunities to investigate a phenomenon, then organize and analyze the gathered data.

The PhET simulation, Gravity Force, can be used to revisit Newton’s Law of Gravitation, modeling masses and their gravitational interactions (Unit 1 Forces and Motion). Leveraging student prior knowledge, educators can present students with a phenomenon that illustrates electrostatic force between two objects (e.g., laser printers). Students can investigate this phenomenon using simulations (e.g., Coulomb’s Law PhET simulation, Coulomb’s Law Lab) to gather information about the observed system (e.g., object types, charges of the objects). 

• By keeping the charges of objects constant and varying the distance between them, students can reveal the inverse square relationship between the gravitational force and “r” (F_e = 1/r²). 

• By keeping the distance between the charges the same and varying the magnitude of one of the charges (e.g., doubling, halving, or tripling one of the charges), students can expose how the electrostatic force is proportional to the products of the charges (F_e = q₁q₂). 

• Organized data include sets of data that hold the charges of the objects constant.

• Organized data include sets of data that hold the separation distance constant.

• Mathematical model indicates the force of electrostatic interaction is inversely proportional to the square of the separation distance F_e = 1/r².

• Mathematical model indicates the force of electrostatic interaction is proportional to the product of the charges F_e = q₁q₂ . 

Provide students with accurate explanations of science ideas to further support an explanation of the phenomenon.

Educators can introduce Coulomb’s Law to help students quantify their observations of the interacting objects. Educators may need to provide additional guidance to help students finalize Coulomb's Law with the proportionality constant (k_e = 8.99 x 109 N m²/C²). Using the given mathematical representation, students can identify and describe the electrostatic force between two objects as the product of their individual charges divided by the separation distance squared (F_e = k(q₁q₂/d²)), where a negative force is understood to be attractive. Students can also use the mathematical representations as evidence that an electric field can cause both attraction and repulsion because electric charge can be either positive or negative.

• Mathematical models are used to correctly predict the electrostatic force between charged objects. 

Provide students with opportunities to compare and contrast phenomena using prior knowledge.

Educators can direct students to use the PhET fields simulation to model the strength and direction of electric forces on a “test” charge (the sensor in the sim) due to a “source” charge (a single or collection of + and - charges in the sim) moved into the active area of the simulation. Students can then arrange the test charge so that the net force acting on it is zero.

Comparison of the two systems should reveal similarities and/or patterns supported by earlier work completed using Newton’s Law of Gravitation and Coulomb’s Law of Electrostatics. This is especially so if the charges and masses are integer multiples of one another.  

• Comparisons of systems identify similarities between Newton’s law of gravitation and Coulomb’s law. 

Narrative Part 2 of 2

Essential Question: How could a system be designed to determine if a relationship between electric current and magnetic fields exists? How does the energy of objects change and transfer while interacting in fields?

OAS-S:

PH.PS2.5 Plan and conduct an investigation to provide evidence that an electric current can cause a magnetic field and that a changing magnetic field can cause an electric current.

PH.PS3.5 Develop and use a model of two objects interacting through electric or magnetic fields to illustrate the forces between objects and the changes in energy of the objects due to the interaction.

3-Dimensional Narrative

Evidence of Understanding

Provide students opportunities to gather observational data or information that will support an explanation for the cause(s) for the phenomenon.

Educators can leverage the phenomenon of electric power generators (see phenomenon section above) to engage students with investigating how electric energy is transferred through electric and magnetic fields (e.g. rotational kinetic energy of the turbine converted to electrical energy). Students can begin by using physical items (e.g., carts with magnets) or simulations (e.g., electric field hockey, charges and fields). Students can observe the forces, the changes in position, and the changes in kinetic energy of each object during the interactions. From these observations, students can develop models (e.g., drawings, sketches) that illustrate how the forces and energy change of one of the objects is related to the change in position between the two objects. Students can further refine their models to include electric currents and magnetic fields illustrating how the force created on a second charge or magnet, and/or how changing the position between two charges or magnets changes the energy stored in the system (electric and gravitational potential video). Students can then describe why these effects are causal and not correlational, citing specific cause-effect relationships. 

• Observations describe transfer of energy through electric or magnetic fields in power plants.

• Models illustrate that both electric and magnetic forces between objects are explained by fields which permeate and can transfer energy through space. 

• Models illustrate the relationships between force, energy, and relative position for two objects interacting through electric or magnetic fields.

• Models are used to predict how changing the relative position between objects interacting through electric and magnetic fields affects force between the objects and energy stored in the system.

Provide opportunities for students to plan investigations to gather observational data that can be used as evidence for the cause(s) of a phenomenon.

Educators can provide students with materials to investigate the relationship between electric currents and magnetic fields created around a current carrying wire (circuit simulator, electromagnetic induction, or online simulation). These materials can include loops of wire (solenoids), batteries or electric power sources, ammeters, and magnetic compasses or other magnetic field sensors. Students may design a procedure to determine if an electric current causes a magnetic field. Students may consider variables such as shape of wire, power source used, and location and orientation of the magnetic field sensor. Students can follow their procedure to gather data about current and the magnetic field. Educators may help students in analyzing their data to determine if there is evidence that electric current causes a magnetic field.

Next, educators can provide students with materials to investigate the relationship between changing magnetic fields and current induced in a nearby circuit (example setup or online simulation). These materials can include permanent magnets or electromagnets, compasses or magnetic field sensors, wires and/or solenoids, and ammeters or other current sensors. Students may design a procedure to determine if a changing magnetic field causes an electric current. Students may consider variables such as shape and position of wire, position of current sensors, and method of changing magnetic field, and recording change in magnetic field. Students can follow their procedure to gather data about changes in magnetic field and current in a circuit. Educators may help students in analyzing their data to determine if there is evidence that a changing magnetic field causes an electric current.

To connect back to the phenomenon, educators can provide students with information on electric generators and/or have students create their own generators (e.g., TeachEngineering). Students can use their models of energy in fields and results from their investigations to construct explanations for how generators use electric and magnetic fields to transform kinetic energy into electrical energy. 

• Investigation plans include data that will be collected, experiment set up, and how measurements of electric current and magnetic fields will be taken.

• Investigation provides evidence that an electric current causes a magnetic field.

• Investigation provides evidence that a changing magnetic field causes an electric current.