TOPIC 4.4: ELECTROMAGNETISM - · PDF fileTopic 4: Fields• SENIOR 3 PHYSICS Topic 4.4 – 44 SPECIFIC LEARNING OUTCOME S3P-4-25: Describe and demonstrate the phenomenon of electromagnetism

TOPIC 4.4: ELECTROMAGNETISMThe student will be able to:S3P-4-25: Describe and demonstrate the phenomenon of electromagnetism.S3P-4-26: Diagram and describe qualitatively the magnetic field around a current-

carrying wire. Include: direction and intensity of the field

S3P-4-27: Diagram and describe qualitatively the magnetic field of a solenoid.Include: direction and intensity of the field

S3P-4-28: Describe and demonstrate the function of an electromagnet.Include: common applications of electromagnets

S3P-4-29: Perform a lab to demonstrate that B ∝ I for an electromagnetic field.S3P-4-30: Describe the force on a current-carrying conductor in a magnetic field.

Include: FB = BIl sinθ

S3P-4-31: Define the magnetic field quantitatively as a force per unit currentelement (i.e., B = FB/I l, where Il is a current element).

S3P-4-32: Solve problems, using FB = BIl.

Topic 4: Fields • SENIOR 3 PHYSICS

Topic 4.4 – 44

SPECIFIC LEARNING OUTCOME

S3P-4-25: Describe anddemonstrate the phenomenon ofelectromagnetism.

GENERAL LEARNING OUTCOMECONNECTION

Students will…Understand how stability,motion, forces, and energytransfers and transformationsplay a role in a wide range ofnatural and constructedcontexts(GLO D4)

Notes to the TeacherToday we use electromagnetism in justabout every aspect of our lives that dependson electricity. Electromagnetism works onthe principle that moving charges generatea magnetic field. This magnetic field is thesame force that is demonstrated bypermanent magnets.

The domain theory should be related to themotion of the electron.

DemonstrationHans Christian Oersted’s discovery ofelectromagnetism can be demonstrated byplacing a compass near a current-carryingconductor. The magnetic field around thewire causes the compass to deflect.However, if we turn the current off, thecompass returns to a north-southalignment.

Suspend a 0.5-m long x 0.05-m wide strip ofaluminum foil between the poles of amagnet. Connect a low-voltage power source(0-3 A) to the ends of the foil. The forceacting on the current-carrying aluminumwill “levitate” the foil.

SUGGESTIONS FOR INSTRUCTION

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SENIOR 3 PHYSICS • Topic 4: Fields

SKILLS AND ATTITUDES OUTCOME

S3P-0-4e: Demonstrate acontinuing and moreinformed interest in scienceand science-related issues.



SUGGESTIONS FOR INSTRUCTION SUGGESTIONS FOR ASSESSMENT

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SPECIFIC LEARNING OUTCOMES

S3P-4-26: Diagram and describequalitatively the magnetic fieldaround a current-carrying wire. Include: direction and intensity of thefield

S3P-4-27: Diagram and describequalitatively the magnetic field ofa solenoid.

Include: direction and intensity of thefield

S3P-4-28: Describe anddemonstrate the function of anelectromagnet.Include: common applications ofelectromagnets


Students will…Evaluate, from a scientificperspective, information andideas encountered duringinvestigations and in daily life(GLO C8)

Notes to the TeacherThe magnetic field around a current-carrying wire forms concentric circlesaround the wire. The direction of themagnetic field is given by the “right-hand”rule: When the thumb of the right handpoints in the direction of the conventionalcurrent, the fingers curl around the wire inthe direction of the magnetic field.Note: Some texts use a “left-hand” rule andthe electron current.

If the wire is formed into a loop, themagnetic field around all parts of the wirecontributes to the field in the middle of theloop, making it stronger. The magnetic fieldincreases as we add more loops (solenoid).The field inside the solenoid is moreintense, is constant, and is directed straightthrough the middle of the solenoid. Thedirection of the field is found by the “right-

hand” rule. If the fingers curl in thedirection of the conventional current, thethumb points in the direction of the field.

Teacher DemonstrationVarious experiments and demonstrationscan be used to describe the fields around acurrent-carrying wire. If the wire is woundthrough Plexiglas®, the fields can bedisplayed on the overhead.

The field of a solenoid can be intensified byplacing an iron core inside the solenoid (i.e.,an electromagnet). The permeability of anelectromagnet describes how many timesthe field is intensified with the core.

Student ActivitiesStudents can build a simple electromagnet.


Topic 4.4 – 47


SKILLS AND ATTITUDES OUTCOMES

S3P-0-3b: Describe examples ofhow technology has evolvedin response to scientificadvances, and how scientificknowledge has evolved asthe result of new innovationsin technology.

S3P-0-2b: Propose problems, statehypotheses, and plan,implement, adapt, or extendprocedures to carry out aninvestigation where required.



The concept of electromagnetism can also becombined with learning outcomes from theWaves topic to design, construct (orassemble), test, and demonstrate atechnological device to produce, transmit,and/or control sound waves for a usefulpurpose.


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SPECIFIC LEARNING OUTCOMES

S3P-4-29: Perform a lab todemonstrate that B ∝ I for anelectromagnetic field.

S3P-4-30: Describe the force on acurrent-carrying conductor in amagnetic field.Include: FB = BIl sinθ

S3P-4-31: Define the magneticfield quantitatively as a force perunit current element (i.e.,B = FB/Il, where Il is a currentelement).S3P-4-32: Solve problems, usingFB = BIl.


Students will…Demonstrate appropriatescientific inquiry skills whenseeking answers to questions(GLO C2)

Notes to the TeacherThere are several labs that can be followedto achieve this learning outcome. • The tangent galvanometer lab can be used

to demonstrate the relationship betweencurrent and magnetic fields.

• The current balance can be used to findthe relationship between F, B, I, and l fora wire and can be used to derive the fieldas a force per unit current element.

Student ActivitiesUsing a digital scale, students place twoopposite poles on the balance and zero thebalance. Suspend a wire between the polesand connect to a power source. Themagnetic force on the wire when a currentis in the wire will be equal to the increase inscale reading times 9.8. • Graph the relationship between force and

current element (Il). The slope of the lineis the magnetic field constant B.

• If the length of wire between the poles isincreased (place two additional polesnearby), the force increasesproportionally.

Teacher DemonstrationThe Jumping Wire (HOT wire Caution!)


Topic 4.4 – 49


SKILLS AND ATTITUDES OUTCOMES

S3P-0-2e: Evaluate the relevance,reliability, and adequacy ofdata and data-collectionmethods.Include: discrepancies in dataand sources of error

S3P-0-2g: Interpret patterns andtrends in data, and infer orcalculate linear relationshipsamong variables.


Students will…Demonstrate appropriatecritical thinking and decision-making skills when choosing acourse of action based onscientific and technologicalinformation(GLO C4)

Journal EntriesStudents diagram the field around aconductor, tangent galvanometer, currentbalance.

Performance AssessmentAsk students: If you were a mass (orpositive/negative charge, or a magnet),describe how you would react to being:• near the Earth (remember Bearth)• near a positive charge (which may or may

not be moving)• near a negative charge• sandwiched between two plates• near one pole of a magnet• between two poles of a magnet• inside a solenoid


SUGGESTED LEARNING RESOURCES

Herreman, W. and R. Huysentruyt. (1995)“Measuring the Magnetic Force on aCurrent Carrying Conductor.” The PhysicsTeacher 33.5: 288.

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NOTES

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TOPIC 4.4: ELECTROMAGNETISM - · PDF fileTopic 4: Fields• SENIOR 3 PHYSICS Topic 4.4 – 44 SPECIFIC LEARNING OUTCOME S3P-4-25: Describe and demonstrate the phenomenon of electromagnetism