Unit 9 - Magnetism (1)

Unit 9 - Magnetism

By S Harris

I know...

• how to compare and contrast magnetic interactions.

​​Learning Target

I can..

• apply the knowledge of magnetic fields and forces to explain how a compass works.

Success Criteria

• it is a force of attraction or repulsion due to the motion of the electrons

  • refers to the properties of magnets and their interactions

What is magnetism?​

these are at the ends of a magnet and are where the magnetic field is the strongest.

• because of this when suspended on a string a magnets will position itself to have the strong ends poin​ting north or south (hence why they are labeled N and S on a magnet)

Magnetic Poles

Magnetic Forces

• this is the force that acts between bodies of like electric charge, causing them to separate.

  • like poles of a magnet will repel (push away from) each other because of this property

Repulsion

• the force that acts between oppositely charged bodies, causing them to draw together.

  • opposite poles of a magnet will attract (come together) because of this​ property

Attraction

Multiple Choice

which of the following situations represents an attractive forces between two poles?

• the north end of one magnet pointing to the north end of another magnet

• the north end of one magnet pointing to the south end of another magnet

• the south end of a small magnet pointing to the south end of a large magnet

• region around a magnet that is affected by the magnet.

  • Strongest at the poles

  • the force forms lines that go out of (away from) the North Pole and wrap back around to go in at (towards) the South Pole.

Magnetic Field

How are magnetic field and magnetic force related?

Magnetic force increases as the magnetic field becomes stronger.

• so stronger magnets have stronger magnetic fields​

Multiple Choice

Which magnet has a stronger magnetic field? (MRI machine or fridge magnets)

Which has a stronger magnetic field?

​MRI Machine

• - the magnetic field of an MRI is about 200 times stronger than the magnetic field of a refrigerator magnet.

  • that's why you have to remove all magnetic metal objects before you enter the room to get your MRI.

Magnetic Field

• can be represented by lines of force called magnetic field lines

• ​the closer the magnetic field lines are, the stronger the magnetic field is at that point.

  • they are closer together near the magnet​

• Earth is thought to have a nickel iron core that gives it a magnetic field similar to a bar magnet.​

The earth is kind of like a giant magnet.​

Do magnets attract ALL metal objects?

​NO, there are a few magnetic materials.

Magnets do not attract all metal materials

• ​examples of metals it will not attract:

  • pieces of aluminum foil or gold

• ​examples of metals it will attract:

  • ​iron, cobalt, and nickel

    • these can be made into permanent magnets

    • these are magnetic because they have electron magnetic properties that do not cancel out and so each will behave like a small magnet with its own magnetic field and poles

Ferromagnetic

• these are objects that can be magnetized (iron, nickel, and cobalt)

  • There are 3 types of magnets

    • Lodestone: naturally occurring

    • Artificial: induced magnetism

    • Electromagnet: temporary magnets that are produced by a moving electric current​

Multiple Choice

Which one of the metal materials will a magnet not pick up?

• Cobalt

• Iron

• Aluminum

• the magnetic field that is inside of the magnet is strong enough to prevent the constant motion of atoms in the magnetic domains from bumping the domain out of alignment.

Permanent Magnet​s

• produced when a moving charge creates a magnetic field

• when charged particles are in motion, a magnetic force field (one that is perpendicular to the motion of the particles) is created

Electromagnets