Simple Phenomena Of Magnetism
Aperçu
A magnet can pull a paperclip across a desk without touching it, and a compass needle swings to point north on its own. Behind both is a magnetic field, an invisible region of influence that you can map, explain and put to work in everything from doorbells to electric motors.
In this lesson you will learn the rules of attraction and repulsion between poles, the difference between magnetic and non-magnetic materials and between temporary and permanent magnets, how to draw and plot a magnetic field, and where permanent magnets and electromagnets are used.
Objectifs
- Describe the forces between magnetic poles and between magnets and magnetic materials, including the use of the terms north pole (N pole), south pole (S pole), attraction and repulsion, magnetised and unmagnetised
- Describe induced magnetism
- State the differences between the properties of temporary magnets (made of soft iron) and the properties of permanent magnets (made of steel
- State the difference between magnetic and non-magnetic materials
- Describe a magnetic field as a region in which a magnetic pole experiences a force
- Draw the pattern and direction of magnetic field lines around a bar magnet
- State that the direction of a magnetic field at a point is the direction of the force on the N pole of a magnet at that point
- Describe the plotting of magnetic field lines with a compass or iron filings and the use of a compass to determine the direction of the magnetic field
- Describe the uses of permanent magnets and electromagnets
- [Supplement] Explain that magnetic forces are due to interactions between magnetic fields
- [Supplement] Know that the relative strength of a magnetic field is represented by the spacing of the magnetic field lines
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Évaluation de la leçon
Félicitations, vous avez terminé la leçon sur Simple Phenomena Of Magnetism. Maintenant que vous avez exploré le concepts et idées clés, il est temps de mettre vos connaissances à lépreuve. Cette section propose une variété de pratiques des questions conçues pour renforcer votre compréhension et vous aider à évaluer votre compréhension de la matière.
Vous rencontrerez un mélange de types de questions, y compris des questions à choix multiple, des questions à réponse courte et des questions de rédaction. Chaque question est soigneusement conçue pour évaluer différents aspects de vos connaissances et de vos compétences en pensée critique.
Utilisez cette section d'évaluation comme une occasion de renforcer votre compréhension du sujet et d'identifier les domaines où vous pourriez avoir besoin d'étudier davantage. Ne soyez pas découragé par les défis que vous rencontrez ; considérez-les plutôt comme des opportunités de croissance et d'amélioration.
- Which test reliably shows that a bar is magnetised? A. it is attracted by a magnet B. it repels one end of a known magnet C. it is made of iron D. it is heavy Answer: B
- Magnetic field lines around a bar magnet point: A. from S pole to N pole B. from N pole to S pole C. in random directions D. in circles only Answer: B
- Which material is best for the core of a switchable electromagnet? A. steel B. copper C. soft iron D. plastic Answer: C
- Where is a magnetic field strongest around a bar magnet? A. in the middle B. where the field lines are closest together C. far from the magnet D. where the lines are furthest apart Answer: B
- Which is a non-magnetic material? A. iron B. steel C. cobalt D. copper Answer: D
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Livres recommandés
Pour aller plus loin, ressources libres
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Section de manuel
Magnetic Fields, Field Lines, and Force
Summarize properties of magnets and describe how some nonmagnetic materials can become magnetized
"Physics: Magnetic Fields, Field Lines, and Force" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/physics/pages/20-1-magnetic-fields-field-lines-and-force. Access for free at https://openstax.org/books/physics/pages/1-introduction
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Section de manuel
Ferromagnets and Electromagnets
Only certain materials, such as iron, cobalt, nickel, and gadolinium, exhibit strong magnetic effects. Such materials are called ferromagnetic , after the Latin word for iron, ferrum . A group of materials made from the alloys of the rare earth elements are also used as strong and permanent magnets;
"College Physics: Ferromagnets and Electromagnets" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/college-physics/pages/22-2-ferromagnets-and-electromagnets. Access for free at https://openstax.org/books/college-physics/pages/1-introduction
Publiées par d'autres organisations sous licence libre, créditées comme elles le demandent. Les liens ouvrent leurs sites.
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