Presentation on theme: "Earth’s Magnetic Field Magnetic history A mineral called magnetite was discovered that attracted other pieces of certain metals. They noticed that these."— Presentation transcript:
Magnetic history A mineral called magnetite was discovered that attracted other pieces of certain metals. They noticed that these pieces when rubbed against small pieces of iron would cause those pieces to become magnetized! b
Why was this important? Before magnets, sailors would have to use the stars in the sky to navigate Once they found out that certain metals could be magnetized they put them in compasses. Compasses point to magnetic south An old compass used for navigation Why did that work? What do the compasses point to? Why?
A magnet: is any substance that can attract iron or other magnetic material! Metals attracted to a magnet: Iron, Nickel, Cobalt Metals not attracted to a magnet: Gold, Copper, Brass, Aluminum Naturally occurring magnetic rocks are called: Lodestones Magnets Basic Magnets
Every magnet has two ends. These ends are called---------------poles One end is the north pole and the other is the south pole. The north pole of a magnet is attracted to the south pole of a magnet. Magnetic Attraction
North and south attract to each other but…. North and North repel South and South repel Repel means to push away. Magnetic Repulsion N Attract S S Repel N N Repel S S Repel N N Attract S
Magnetic Fields If you hold magnets you know that they can attract or repel without touching each other. This is because they create a magnetic field. Magnetic fields are regions of magnetic force around a magnet. N S
More Magnetic Fields Draw these magnetic fields in your notes: NN NS SS
How do magnetic fields work? Electrons in an atom spin. Moving electrons produce a magnetic field. (book page 304 figure 4) This makes each atom a tiny magnet. In most materials these fields point in random directions. But, if a cluster of billions of atoms that have magnetic fields that are lined up in the same way it is called a Domain.
How do magnetic fields work? Images to help explain magnetic fields DomainsElectrons
Magnetic Domains These domain parts of a magnetic can line up to all have the same charges face the same direction. This is why some materials like a paper clip can be magnetized. These domain parts of a magnetic can line up to all have the same charges face the same direction. This is why some materials like a paper clip can be magnetized.
The Earth as a Magnet The Earth is actually a big magnet. The Earth’s magnetic field is called the magnetosphere. – Earth’s magnetic North and South poles are actually not the same as the geographic poles. The difference between the two is called the magnetic declination. – Theory is that the Earth’s core is what generates this field
Earth’s Magnetic Field This magnetic field around Earth protects us from charged particles the sun produces that could harm us. ~700,000 years ago the north and south magnetic poles switched on the planet. Evidences is shown in our rock record.
Electromagnets Magnetic fields are produced by moving electric charges, the electrons moving around the nucleus of an atom. You can create a magnet by using coiled wire, a voltage source and a magnetic material. Electromagnet: is a current-carrying wire wrapped around an iron core.
More Electromagnets The magnetic field of an electromagnet is turned off when the electric current stops. If you change the direction of the current you can change the strength and direction of the magnetic field.
Uses for Electromagnets Generators use magnetic fields to turn motion into electricity. – Generators: kinetic energy is changed into electric energy – Motors: electric energy is changed into kinetic energy. Both of these can use magnets
Superconductors When most conductors of electricity have a current flowing through them they heat up. Some objects that are cooled to very cold temperatures become superconductors which have no resistance to electric flow. They produces a magnetic field opposite to that of regular magnets and will repel them.
Note Quiz 1.What is a benefit about having a magnetic field around Earth? 2.Define Electromagnet. 3.The difference between the geographic north pole and the magnetic north pole is called?
Note Quiz 1.What do north poles of magnets attract, what do they repel? 2.What is the definition of a magnetic field? 3.Draw a diagram of a magnetic domain? You are allowed to use your notes. Make sure all answers are on a half sheet of paper and your name is in the upper right hand corner of the sheet.