Magnetism Unit Notes 1
description
Transcript of Magnetism Unit Notes 1
![Page 1: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/1.jpg)
Magnetism UnitNotes 1
Grade 10 ST
![Page 2: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/2.jpg)
Magnetic Behaviour
• After watching the demo, what conclusions can you make about what you saw?
______________________________________________________________________________________________________________________________________________________________________________________________________________________________
![Page 3: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/3.jpg)
What is Magnetism?
• Magnetism is the force of attraction or repulsion in and around a material
• Magnetism is present in all materials but at such low levels that it is not easily detected
• Certain materials such as magnetite, iron, steel, nickel, cobalt exhibit magnetism at levels that are easily detectable
![Page 4: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/4.jpg)
What is a Magnet?
• A magnet is any piece of material that has the property of attracting iron (or steel).
• Magnetite, also known as lodestone, is a naturally occurring rock that is a magnet.
• This natural magnet was first discovered in a region known as Magnesia in Greece and was named after the area in which it was discovered.
![Page 5: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/5.jpg)
What is a Magnet? Cont’d
• Magnetism may be naturally present in a material or the material may be artificially magnetized by various methods.
• Magnets may be permanent or temporary.– After being magnetized, a permanent magnet will
retain the properties of magnetism indefinitely.– A temporary magnet is a magnet made of soft iron,
that is usually easy to magnetize; however, temporary magnets lose most of their magnetic properties when the magnetizing cause is discontinued.
![Page 6: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/6.jpg)
Different Types of Magnetic Materials
Magnetic• A permanent magnet• Two magnetized objects can attract or repel
each other
![Page 7: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/7.jpg)
Different Types of MagneticMaterials
Ferromagnetic• Materials which can be magnetized are called ferromagnetic
materials • They contain iron, nickel or cobalt• They are attracted to magnetic objects, they become temporarily
magnetized• Example: Iron
– Iron is made up of a set of regions called domains.– Each domain acts like a tiny magnet with it’s own north and south poles– When iron is not magnetized= domains are not aligned– When iron is magnetized domains are aligned
![Page 8: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/8.jpg)
Different Types of MagneticMaterials
Non- magnetic• Non-magnetic objects do not react to the
presence of a magnet. They are not attracted or repelled!
![Page 9: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/9.jpg)
Temporary vs. Permanent Magnets
![Page 10: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/10.jpg)
Magnetic Properties• http://www.ndt-ed.org/EducationResources/HighSchool/Magnetism/magnetic
properties.htm
• After watching the above applet, explain what happens when a magnet is broken into smaller pieces
____________________________________________________________________________________________________________________________________________________
![Page 11: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/11.jpg)
Magnetic Properties
• Magnets can be cut into smaller and smaller pieces indefinitely
• All magnets have a north seeking and south seeking pole
• Each new piece makes a new magnet with it’s own north and south poles.
• The NORTH POLE of a magnet is the end that naturally seeks the earth’s magnetic pole near the geographic north pole
![Page 12: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/12.jpg)
Magnetic Properties
• Magnets interact with each other through forces of attraction and repulsion
• In general, the following is true of magnetic poles– Opposite magnetic poles attract– Like magnetic poles repel each other
Question: Knowing this, is the North Pole a North Pole or a South Pole? _____________________________
![Page 13: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/13.jpg)
Magnetic Properties Check
• If the north pole of a magnet is moved toward the south pole of another magnet, will the north pole be subjected to an attractive or a repulsive force? Explain your answer.
____________________________________________________________________________________________________________________________________________________
![Page 14: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/14.jpg)
Interesting Article
• http://www.scientificamerican.com/article.cfm?id=cattle-deer-sense-magnetic-field&print=true
![Page 15: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/15.jpg)
Magnetic Fields
• In a magnetized object, the domains are all lined up in the same direction.
• Any magnetized object produces a magnetic field. The magnetic field is the area around the magnet where the magnetic force can be felt.
![Page 16: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/16.jpg)
Magnetic Fields
• To draw the magnetic field, we use arrows.• Most magnets have 2 poles: north (N) and
south (S)• Two possible forces exist between
magnetized objects• Attraction• Repulsion
![Page 17: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/17.jpg)
Magnetic Field around a bar magnet•Arrows are always pointing towards the south
![Page 18: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/18.jpg)
Compasses
How do compasses work?• The north needle of a
compass always points in the same direction as the magnetic field.
![Page 19: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/19.jpg)
Magnetic field around a straight wire
• When there is a current flowing through a wire, there is a magnetic field around the wire.
• The shape of the magnetic field is individual circles around the wire.
![Page 20: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/20.jpg)
Magnetic Field around a Straight Wire
To determine the direction of the magnetic field lines we use the “Right Hand Rule”
• Place your right thumb along the direction of the current.
• Your fingers curl in the same direction as the magnetic field
![Page 21: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/21.jpg)
Magnetic Field around a Straight Wire
Try it…
_ +
![Page 22: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/22.jpg)
Magnetic Field around a Straight Wire
• In a circuit • With Compass
![Page 23: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/23.jpg)
Magnetic Field around Electromagnets
• When there is a current flowing through a coiled wire, there is a magnetic field that is created we call it an electromagnet.
• The shape of the magnetic field around the electromagnet is exactly the same as around a bar magnet
![Page 24: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/24.jpg)
Magnetic Fields around Electromagnets
• To determine the location of N and S, we use the “Second Right Hand Rule”
• Place your fingers on your right hand so that they curl in the same direction as the current.• Your thumb indicates north
![Page 25: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/25.jpg)
Magnetic Fields around Electromagnets
• Try it… • With Compass
![Page 26: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/26.jpg)
Factors that affect the strength of an electromagnet
• To increase the strength of an electromagnet:– Increase current– More coils– Type and gauge of the conductor– The core material
![Page 27: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/27.jpg)
Induction in an Electromagnet
• To generate a magnetic field:
![Page 28: Magnetism Unit Notes 1](https://reader035.fdocuments.us/reader035/viewer/2022081422/568165de550346895dd8f956/html5/thumbnails/28.jpg)
Induction in an Electromagnet
• To generate an electric current: