1. Attraction and Repulsion Magnetism and Its Uses

2. Magnetism Discovered over 2000 years ago in Magnesia, TurkeyDiscovered over 2000 years ago in Magnesia, Turkey Magnetic ForceMagnetic Force –You can feel the magnetic ability before magnets touch Magnetic FieldMagnetic Field –Surrounds the magnet –North and South pole is strongest point Round magnet has poles on the top and bottomRound magnet has poles on the top and bottom –Field has direction north to south

3. Unlike poles attractUnlike poles attract –Produce new magnetic field Like poles that are the same Like poles that are the same –Repel Magnetic Field DirectionMagnetic Field Direction –Goes from north to south

4. Earth’s Magnetic Field South Seeking Pole  North Geographic Pole North Seeking Pole  South Geographic Pole Reason for earth’s magnetism is unknown magnetism is unknown

5. Magnetic Materials Iron, cobalt and nickel are naturally magneticIron, cobalt and nickel are naturally magnetic –Electron’s magnetic properties not cancelled in these metals –Each atom magnetic –Not always magnetic –Groups of atoms must be aligned Called Magnetic DomainCalled Magnetic Domain

6. Even though each domain behaves like a magnet, the poles of the domains are arranged randomly and point in different directions. Lining Up Domains 8.1 Magnetism As a result the magnetic fields from all the domains cancel each other out.

8. If you place a magnet against the same nail, the atoms in the domains orient themselves in the direction of the nearby magnetic field. Lining Up Domains 8.1 Magnetism The like poles of the domains point in the same direction and no longer cancel each other out.

9. Domain alignment can be temporary or permanentDomain alignment can be temporary or permanent –Magnet held next to metal will align domain –Vibrations/Heat will knock domain out of alignment Permanent magnets have strong magnetic domain not influenced by atomic motionPermanent magnets have strong magnetic domain not influenced by atomic motion

10. Electricity and Magnetism

11. Electric currents creates a magnetic fieldElectric currents creates a magnetic field Magnetic field reverses when the current reversesMagnetic field reverses when the current reverses ElectromagnetElectromagnet –Temporary –Solenoid-cylindrical wire coil –Strength determined by coil –Speakers and motors (Electric to Mechanical)

12. Moving Charges and Magnetic Fields It is now known that moving charges, like those in an electric current, produce magnetic fields. Around a current-carrying wire the magnetic field lines form circles. 8.2 Electricity and Magnetism

14. Increasing Coils Increasing Current  Larger Magnetic Field

15. Faraday’s Law Flux in magnetic force=flux in electric voltageFlux in magnetic force=flux in electric voltage

16. Using Electromagnets to Make Sound The electromagnet changes electrical energy to mechanical energy that vibrates the speaker cone to produce sound. 8.2 Electricity and Magnetism

17. Using Galvanometers In a galvanometer, the electromagnet is connected to a small spring. 8.2 Electricity and Magnetism Then the electromagnet rotates until the force exerted by the spring is balanced by the magnetic forces on the electromagnet.

18. A Simple Electric Motor A simple electric motor also includes components called brushes and a commutator. 8.2 Electricity and Magnetism The brushes are conducting pads connected to the battery. The brushes make contact with the commutator, which is a conducting metal ring that is split. The brushes and the commutator form a closed electric circuit between the battery and the coil.

19. Making the Motor Spin Step 1. When a current flows in the coil, the magnetic forces between the permanent magnet and the coil cause the coil to rotate. 8.2 Electricity and Magnetism

20. Making the Motor Spin Step 2. In this position, the brushes are not in contact with the commutator and no current flows in the coil. 8.2 Electricity and Magnetism The inertia of the coil keeps it rotating.

21. Making the Motor Spin Step 3. The commutator reverses the direction of the current in the coil. 8.2 Electricity and Magnetism This flips the north and south poles of the magnetic field around the coil.

22. Making the Motor Spin Step 4. The coil rotates until its poles are opposite the poles of the permanent magnet. 8.2 Electricity and Magnetism The commutator reverses the current, and the coil keeps rotating.

23. Superconductors-mercury, lead and tinSuperconductors-mercury, lead and tin Conductors-copper and aluminumConductors-copper and aluminum Semiconductors-siliconSemiconductors-silicon Credit Card Magnetic StripCredit Card Magnetic Strip

24. Producing Electricity From Mechanical to ElectricalFrom Mechanical to Electrical Electromagnetic inductionElectromagnetic induction GeneratorGenerator –Coil rotates between the poles of a permanent magnet –Rotations change the direction of the current – Rotate 60 times a second-How many times per minute?

25. Types of Electrical Currents Direct CurrentDirect Current –Battery –Current in one direction Alternating currentAlternating current –Household current –Current changes direction 2x per second –Produce at 60 Hz per second –How many times does direction change per minute?

26. TransformersTransformers –150,000 volts generated by power plants –Too much for house –Voltage needs to be lowered