Lines of force shape pole

Transcription

1 Discuss What is a Magnet? Magnetism: a force of attraction or repulsion by magnetic materials. Are not Copper, plastic, and glass attracted to magnets. are Steel, cobalt, iron, and nickel attracted to magnets. Pole: the ends of a magnet where the forces are strongest. 2 north south Every magnet has poles: a pole and a pole. If a magnet is broken into pieces, each piece will still have poles. 2 Poles behave similarly to electric charges. attract Opposites and likes. attract A north and a south will. repel Two north poles will. repel repel Two south poles will. What causes magnetism? Magnetic Field Lines: the region of magnetic force around a magnet. It causes attraction between the magnet and another object. A magnetic field is made up of. These lines of force will show the of a magnetic field. Magnetic lines of force begin at one and end at the other pole. Lines of force shape pole

2 They are closest together at the, where the field is the strongest. poles N S N S Magnetic lines of force from the South and North poles will bend towards each other. Magnetic lines of force from two South poles or two North poles will bend away from each other. N S S N

3 Magnetic Domains: groups of atoms whose magnetic poles line up in the same direction. When materials are magnetized, the magnetic domains point in the same direction different When materials are NOT magnetized, the domains point in directions. Not Magnetized Magnetized Domains NOT Aligned Domains Aligned How Can You Make A Magnet? Magnetic Induction: the process by which a material can be made into a magnet. Materials can be magnetized by being rubbed in direction with a magnet. Materials become magnetized when the point in the same direction. Not all materials respond in the same way to the magnetic field. Natural Magnets: magnets that occur in Temporary Magnets: Magnets that are magnetized easily but lose the magnetism easily as well. Permanent Magnets: Magnets that are difficult to magnetize but they keep the magnetism well. lose one domains nature All magnets can their magnetism. Dropping, hitting or heating the magnet can demagnetize it because the domains become unaligned.

4 How is Earth like a Magnet? A British scientist named Wilbert Gilbert suggested that Earth is a magnet when he observed a magnet hanging from a string will align its north and south poles with the north and south poles of the Earth. The Earth s Magnetic Poles 2 Earth has magnetic poles. Close to Magnetic poles are, but not the geographic poles. What we call the Earth s north pole is actually the magnetic pole. What we call the Earth s south pole is actually the magnetic pole. When a compass points north its is because the compass s north pole is attracted to the at Earth s magnetic south pole, which we call the north pole. south north The Magnetosphere: the magnetic field around the Earth. The magnetosphere traps some charged particles from the sun that interact with other particles in the atmosphere, causing the air above Earth to glow. This is called an aurora.

5 How are electricity and magnetism related? Oersted s Discovery The relationship between electricity and magnetism is called electromagnetism. Hans Christian Oersted noticed that when current flowed through a wire, a nearby compass pointer. Deflected (moved) He discovered that an electric current produces a magnetic field. Electromagnetic Induction: Does a magnetic field produce an electric current? Michael Faraday brought a strong magnet near a still wire. o If the magnet remains stationary, then current Will not flow through the wire. o If the magnet moves toward or away from the wire continuously, then current will flow through the wire. o If a coil of wire moves toward or away from a magnet, then current Will flow through the wire. The process by which an electric current is produced in a wire when the wire is exposed to a Electromagnetic induction changing magnetic field is called. o The changing magnetic field is often changing due to relative movement. The wire and the magnet need to move relative to each other.

6 What is an electromagnet? A wire carrying an electric current always has a field around it. o The field around a straight wire is very weak. o However, if the wire is wound into a coil, the magnetic field becomes much. An electromagnet is a magnet made by wrapping a current-carrying wire around a metal. It is called temporary because when the current is turned off, there is no longer a magnetic field. Increasing the strength of the electromagnet: There are three major ways to increase the strength of the electromagnet: o Increase the number of. o Increase the amount of. o Adding a metal. What is an electric motor? Magnetic stronger An electric motor converts energy into mechanical temporary core core coils current electrical energy. magnetic Rotation is created by alternating between attraction and repulsion between a current carrying wire and a permanent magnet. o Alternating current. o On and Off Direct current.