Download Strength of an Electromagnet

Primary Type: Lesson Plan
Status: Published
This is a resource from CPALMS (www.cpalms.org) where all educators go for bright ideas!
Resource ID#: 71380
Strength of an Electromagnet
In this guided-inquiry lesson for advanced students in high school physics or integrated science classes, students will have an opportunity to conduct
an experiment to test how the strength of an electromagnet can be affected by different variables. Students will derive equations from their data.
Subject(s): Science
Grade Level(s): 9, 10, 11, 12
Intended Audience: Educators
Suggested Technology: Document Camera, LCD
Projector, Microphones
Instructional Time: 2 Hour(s) 30 Minute(s)
Resource supports reading in content area: Yes
Freely Available: Yes
Keywords: Charge, Current, Voltage, Electric Field, Electromagnet, Force,
Instructional Design Framework(s): Guided Inquiry (Level 3), Writing to Learn
Resource Collection: FCR-STEMLearn Physical Sciences
LESSON CONTENT
Lesson Plan Template: General Lesson Plan
Learning Objectives: What should students know and be able to do as a result of this lesson?
Students will be able to:
1. Explain how the strength of an electromagnet would be affected by the amount of the current.
2. Graph the relationship between the amount of current and the number of paper clips (or the total mass of paper clips) being attracted by the tip of an iron nail.
3. Graph the relationship between the amount of number of coils surrounding an iron nail and the the number of paper clips being attracted by its tip.
4. Predict the amount of current for an electromagnet needed to attract a specific amount of paper clips.
5. Derive a formula based on their calculations.
Prior Knowledge: What prior knowledge should students have for this lesson?
1. Students must have a basic understanding of current, voltage, electric charges, and electric fields.
2. Students should know how to manipulate a multimeter to measure current and voltage.
Guiding Questions: What are the guiding questions for this lesson?
1. What factors affect the strength of an electromagnet?
2. How can the forces acting on an electromagnet be measured and compared?
Teaching Phase: How will the teacher present the concept or skill to students?
Background information on electromagnets for the teacher has been provided.
Show the video clip going to the scrap yard which shows an electromagnet picking up junk wheel rims.
After watching the video, have students discuss what they observed. How does an electromagnet work? Introduce the lesson.
The teacher will present the guiding question to the students: What factors affect the strength of an electromagnet?
Preview some of the definitions involved in electricity:
current
page 1 of 5 power
voltage
What are the variables involved in using an electromagnet? (material, electricity, conductor, power source) How do we measure them?
Focus on each item one at a time.
1. Battery: What affect would more or less batteries have on an electromagnet?
2. Wire: What affect would longer wire have on an electromagnet? What about a thicker wire? What about the material of the wire? How about the way the wire is
arranged?
In this exploration, students will explore the factors that affect the strength of an electromagnet. For this, they must know how to use a multimeter. Review this with
students. If needed, the teacher might show the multimeter tutorial video from Afrotechmods; start at 1:04.
Review how to measure the current and voltage across a simple circuit.
Assign students to their lab groups and provide them with their lab directions. Review your lab safety guidelines.
Guided Practice: What activities or exercises will the students complete with teacher guidance?
Have the following materials ready at each lab station:
Multimeter
Four D batteries
Copper wire of several lengths and thicknesses
Resistors
Iron nail
Paper clips
Keep the length of the wire the same throughout the investigation. It is also important to keep a consistent distance between the end of the wire and the tip of the nail.
Students will create an electromagnet while following throughout the guidelines on the lab sheet. A sample diagram is attached.
1. The teacher will be walking around the classroom to observe their students and assist if needed. For example, if a student asks how the paper clips should connect
to one another, the teacher can instruct students to let the paper clips hang along a vertical line.
2. To address a possible safety concern, the teacher can provide one rheostat or another resistor and direct students to connect it to the circuit (i.e., 100 up to 300
ohms) to prevent the wire from getting too warm and avoid a short-circuit.
3. A document with background information about current electricity and magnetism is attached.
Independent Practice: What activities or exercises will students complete to reinforce the concepts and skills developed in the
lesson?
1. As students work through the investigation, the teacher should remind students to try to identify any patterns. Relate the math back to their data. What does it
mean? Can they find a correlation? Is it a direct relationship? An inverse relationship?
2. The teacher can use the activity on Magnets and Electromagnets available from PhET Interactive Simulations to reinforce how the magnetic field strength would be
affected by the number of turns of the coil, the amount of flowing current, and the amount of voltage. Students also can draw the relationship between the current
(as indicated by the compass needle) and the magnetic field.
Closure: How will the teacher assist students in organizing the knowledge gained in the lesson?
1. At the end of this class, the teacher will ask each group to present their findings to the class. If any discrepancies are uncovered between the findings of one group
and those of the rest of the class, look at any possible source of error.
2. In the final portion of this lab, students combine the two explorations into one, and note that even though they are directly proportional, they don't equal each other.
This leads to the idea of a constant (Kµ0) to help balance the equation.
FB = Kµ0 (nI)
Finally, return to the video of the industrial electromagnet in the junkyard. Can you think of other applications of electromagnetic technology?
Summative Assessment
Students will be completing a lab sheet that walks them through the exploration of the concept, including their final formula and explanation of how the factors are
related.
Formative Assessment
The teacher will guide students throughout the lesson as they explore the concepts.
At each stage of the lab, the teacher will facilitate and redirect as necessary.
Check for understanding and usage of proper terminology. This will be important as students move into more difficult aspects of the exploration and while using the
formulas.
Feedback to Students
Within this guided inquiry lesson, students are required to work in groups to solve the given problems.
The teacher will assist the students to make sure they are on the right track.
If needed, the teacher will have a whole class discussion about their common questions.
A scoring rubric will be given to students to help them throughout the lesson.
ACCOMMODATIONS & RECOMMENDATIONS
Accommodations: The teacher needs to be mindful when grouping students to ensure there is a balance of students with various ability and skills in each group.
page 2 of 5 Extensions: The teacher could have students build a simple motor to demonstrate how they can apply their knowledge beyond this lab activity.
Suggested Technology: Document Camera, LCD Projector, Microphones
Special Materials Needed:
Per student:
Lab sheet
Per student group:
Four D batteries
One resistor
One iron nail
Copper wire
Wire cutter
Several paper clips
Further Recommendations: After students have completed this lesson, the following CPALMS Perspectives video can be used to see another real-world
application of electromagnets: an archeologist who uses ground-penetrating radar.
If you need help in the content or pedagogical support, the following URL links might be helpful:
1. Magnets and Ion Core Solenoid from HyperPhysics
2. Solenoid and Magnetic Field Equations from HyperPhysics
3. 2D Magnetic Field Demonstrations from UniServeScienceVIDEO
Additional Information/Instructions
By Author/Submitter
This lesson incorporates the following mathematical practice standards:
MAFS.K12.MP.1: Make sense of problems and persevere in solving them.
MAFS.K12.MP.2: Reason abstractly and quantitatively.
MAFS.K12.MP.3: Construct viable arguments and critique the reasoning of others.
MAFS.K12.MP.4: Model with mathematics.
MAFS.K12.MP.6: Attend to precision
SOURCE AND ACCESS INFORMATION
Contributed by: ChinTang Liu
Name of Author/Source: ChinTang Liu
District/Organization of Contributor(s): Broward
Is this Resource freely Available? Yes
Access Privileges: Public
License: CPALMS License - no distribution - non commercial
Related Standards
Name
SC.912.P.10.16:
Description
Explain the relationship between moving charges and magnetic fields, as well as changing magnetic fields and electric
fields, and their application to modern technologies.
Remarks/Examples:
Explain that moving electric charges produce magnetic forces and moving magnets produce electric forces.
Recognize the Lorentz force is the force on a point charge due to electromagnetic fields and occurs in many
devices, including mass spectrometers.
Attached Resources
Virtual Manipulative
Name
Battery-Resistor Circuit:
Description
This simulation demonstrates how a resistor works and the relationship between voltage, current and resistance. A
change in temperature is also recorded with varying the parameters.
The students will be shown the flow of electrons to make a fan spin. The more resistance that they put the slower the
elctrons will move and vice versa. The students will also see the power generated by the battery.
An electronic 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 lifelike view.
Other options for exploration:
Discuss basic electricity relationships
page 3 of 5 Circuit Construction kit:
Build circuits from schematic drawings.
Use an ammeter and voltmeter to take readings in circuits.
Provide reasoning to explain the measurements and relationship in circuits.
Discuss basic electricity relationships in series and parallel circuits.
Provide reasoning to explain the measurements in circuits.
Determine the resistance of common objects in the "Grab Bag".
Circuit Construction Kit:
The students will have the opportunity to build their own circuit loop with the materials presented to them.
Generator:
This virtual manipulative will help the students generate electricity with a bar magnet. Students can discover the physics
behind the phenomena by exploring magnets and how they can be used to make a bulb light. They will recognize that
any change in the magnetic environment of a coil of wire will cause a voltage to be induced in the coil.
Some of the sample learning goals can be:
Identify equipment and conditions that produce induction.
Compare and contrast how both a light bulb and voltmeter can be used to show characteristics of the induced
current.
Predict how the current will change when the conditions are varied.
Explain practical applications of Faraday's Law.
Explain what is the cause of the induction.
This virtual manipulative will allow the students to explore the interactions between a compass and bar magnet.
Students can discover that magnetic fields are produced when all the electrons in a metal object are spinning in the
same direction, either as a natural phenomenon, in an artificially created magnet, or when they are induced to do so
by an electromagnetic field.
Some of the sample learning goals can be:
Magnets and Electromagnets:
Predict the direction of the magnet field for different locations around a bar magnet and electromagnet.
Compare and contrast bar magnets and electromagnets.
Identify the characteristics of electromagnets that are variable and what effects each variable has on the magnetic
field's strength and direction.
Relate magnetic field strength to distance quantitatively and qualitatively.
Ohm's Law:
This virtual manipulative will allow the user to see how the equation form of ohm's law relates to a simple circuit.
Learners can adjust the voltage and resistance, and see the current change according to Ohm's law. The size of the
symbols in the equation change to match the circuit diagram.
Resistance in a Wire:
This manipulative will help the students to learn about the physics of resistance in a wire. The electrical resistance of a
wire would be expected to be greater for a longer wire, less for a wire of larger cross sectional area, and would be
expected to depend upon the material out of which the wire is made, to understand this, students can change the
resistivity, length, and area to see how they affect the wire's resistance. The sizes of the symbols in the equation
change along with the diagram of a wire.
Some of the sample learning goals can be:
What characteristics of a resistor are variable in this model?
How does each affect the resistance (will increasing or decreasing each make the resistance correspondingly
increase or decrease?)
Explain your ideas about why they change the resistance.
Learn how to build a circuit
Virtual Construction Kit (DC
only):
Learn how to measure voltage in a circuit using a voltmeter
Determine the resistance of certain objects that can be used as part of an electric circuit
Explain the difference between parallel and series circuits
Video/Audio/Animation
Name
Description
Learn how to build a circuit
Show the difference between AC and DC
Circuit Construction Kit (AC +
Describe the effect of an inductor on a circuit
DC):
Describe the effect of a capacitor on a circuit
Learn how to use an ammeter and a voltmeter in a circuit
Resource Collection
Name
Exploring Magnetism Lesson
Series:
Description
"These seven NASA-funded magnetism guides contain activity- or math-based lessons on magnetic fields. The science
and mathematics education standards these activities cover are in the beginning of the guides... These guides were
developed as part of the Education and Public Outreach programs of the following NASA science missions: STEREOIMPACT, RHESSI, THEMIS, and FAST."
These are modules, including student worksheets, about magnetism in general and especially about the Earth's
magnetic field.
page 4 of 5 Lesson Plan
Name
Magnetism:
Description
Students investigate magnetism and which materials are attracted by magnets. Students describe the behavior of
atoms in a magnet and explain why specific materials are or are not attracted to a magnet. The discussion questions
explore several domains of science and relate them to magnetism.
page 5 of 5