Chapter 3; Lesson 3.1

T.O.C

Magnetism is a Force that acts at a Distance

Magnets attract & repel other Magnets

• Magnets(w.w) object that attracts certain other materials, like iron & steel

• Magnetism(w.w) force exerted by a magnet–Magnets do not have to touch objects to

exert a force on it. (Like gravity/static electricity)

– Ex: refrigerator door–Magnetism is the result of a moving electric

charge.

https://www.youtube.com/watch?v=EKkUA52NEYQ

What is happening

in each photo?

Continued….• The force of magnetism is not evenly distributed

throughout a magnet.• Magnetic Poles(w.w) the parts of a magnet

where the magnetism is the strongest.– Every magnet has a north-seeking pole. The other is

the south pole.– Like electricity; opposite poles attract & like poles

repulse

• Magnetic Field(w.w) region around a magnet in which the magnet exerts force.– The arrangement of magnetic field lines depends on

the shape of the magnet.– Magnetic field lines always start at N. & end at S.

*Iron filings/magnetic field DEMO*

Some Materials are Magnetic

• Inside nonmagnetic/magnetic materials:– In materials that are not magnetic, like

wood, the magnetic fields of the atoms are weak & point in different directions cancelling out the magnetic field.

– In materials that are magnetic, such as iron, magnetic fields of a group of atoms align & point in the same direction.

–Magnetic Domain(w.w) group of atoms whose magnetic fields are aligned.

– A magnet is a material in which the magnetic domains are all aligned.

*Lab- Is it Magnetic?*

Temporary v. Permanent Magnets• If you bring a magnet near a paperclip containing iron,

the magnet pulls the paperclip towards it. This aligns the paperclip atoms & creates a magnetic field. OBSERVE *demo*

• Remove the magnet → the paperclip chain dissolves• The paperclip chain is a TEMPORARY magnet.• A permanent magnet can be created by placing

magnetic materials inside a strong magnetic field, or by repeatedly stroking a piece of magnetic material in the same direction w/ a strong magnet.

*Demo- Permanent magnet*1- find North on compass. Align iron nail.2- heat iron nail. Remove from heat keeping aligned.3- stroke with strong magnet in only one direction.4- when the iron nail cools, it will be magnetized.

Earth is a Magnet

• An easy way to see this is w/ a compass. They will always point N.

• The magnetic field of Earth acts like a large bar magnet that runs thru Earth’s axis.

• The source of Earth’s magnetic field is the motion of its core, which is mostly composed of iron & nickel charged particles.

• Earth’s magnetic field affects all magnetic materials around you!

• Earth’s magnetic poles can reverse! Has happened about 400 times. – Evidence: shown in layers of rocks on the ocean

floor. Iron in minerals line up w/ the poles. *Lab- create a compass*

Magnetism & the Atmosphere

• A constant stream of charged particles is released by reaction inside the Sun.

• These particles could damage living cells if they reached Earth’s surface.

• Earth’s magnetic field deflects this flow of charged particles.

• Many of these particles are deflected toward the magnetic poles of Earth. As they approach, the particles react w/ Oxygen & Nitrogen in Earth’s atmosphere.

• These reactions can be seen at night as vast moving sheets of color that can fill the whole sky. These are the Northern or Southern Lights.

3.1 Review Q’s 10 pts1. Why are some materials magnetic & not

others? (2 pts)2. What force causes magnets to attract/repel

one another? (2 pts)3. What is the source of Earth’s magnetic field?

(2 pts)4. Where is the magnetic field of a magnet the

strongest? (2 pts)5. How can the maglev train operate without

touching the tracks? (2 pts)