Warm Up What is a current? What is the difference between an open and closed circuit? What are parallel and series circuits? Warm Up

Brainpop: Magnetism http://www.brainpop.com/science/motionsforcesandtime/magnetism/preview.weml

Magnetism is a Force That Acts at a Distance Before, you learned Now, you will learn A force is a push or a pull Some forces act at a distance Atoms contain charged particles How magnets attract and repel other magnets What makes some materials magnetic Why a magnetic field surrounds Earth

A Magnet… Always has a north pole and a south pole (dipole) Like poles repel Unlike poles attract

A Magnet… Always has a north pole and a south pole (dipole) Like poles repel Unlike poles attract Has a magnetic field Exerts a force on other magnets in the direction of the magnetic field Is 3-dimensional Exists inside and outside of the magnet The magnetic field of a magnet is strongest at the poles

Magnetic Fields

Earth is a magnet The magnetic field around Earth acts as if there were a large bar magnet that runs through Earth’s axis. The source of Earth’s magnetic field is the movement in the core, which is mostly iron and nickel The Northern Lights and Southern Lights occur near Earth’s magnetic poles, because these locations are where Earth’s magnetic field is strongest.

A Magnet… Always has a north pole and a south pole (dipole) Like poles repel Unlike poles attract Has a magnetic field Exerts a force on other magnets in the direction of the magnetic field Is 3-dimensional Exists inside and outside of the magnet Induces magnetism in some materials (induced magnetism) Magnetism – the force exerted by a magnt Causes metals to act like magnets, thus causing pole attraction/repulsion Can be demagnetized several ways including: Placing into a large magnetic field Banging on concrete

Types of Magnets

Permanent Magnets Placing magnetic materials in very strong magnetic fields makes permanent magnets

Bar Magnets (chrome-steel alloy) Permanent Magnets Bar Magnets (chrome-steel alloy) Horseshoe Magnets (nickel-cobalt-iron alloy) Refrigerator magnets!

Temporary Magnets Iron Nails Paper Clips

Magnetic Materials In a material that is not magnetic, the magnetic fields of the atoms are weak and point in different directions. In a material that is magnetic, the magnetic fields of a group of atoms align, or point in the same direction. A magnetic domain is a group of atoms whose magnetic fields are aligned. A magnetic is a material in which the magnetic domains are all aligned.

Review What force causes magnets to attract or repel one another? Why are some materials magnetic and not others? Describe three similarities between Earth and a bar magnet? A needle is picked up by a magnet. What can you say about the needle’s atoms? The Northern lights can form into lines in the sky. What o you think causes this effect?