1 / 30

Magnetism

Magnetism. What is the relationship between magnetism and electricity?. Jack T. Duncan Physical Science. EQ1: What is magnetism?. Magnetism – the properties and interactions of magnets 1. All magnets have magnetic forces – ability to attract or repel.

yehuda
Download Presentation

Magnetism

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Magnetism What is the relationship between magnetism and electricity? Jack T. Duncan Physical Science

  2. EQ1: What is magnetism? • Magnetism – the properties and interactions of magnets 1. All magnets have magnetic forces – ability to attract or repel. 2. The magnetic field surrounds a magnet and exerts magnetic lines of force. - stronger when closer to magnet

  3. EQ2: How do magnets behave? • Magnetic poles – regions of magnet where the magnetic forces are the strongest - magnetic lines are the most numerous 1. All magnets have a north(N) and south(S) pole. - Two unlike poles (N-S) – attract - Two like poles (N-N & S-S) – repel * make drawings

  4. Earth’s magnetic poles 2. The earth has north and south magnetic poles. - different locations than the earth’s geographic poles ( N magnetic pole – Canada) - the compass – is a freely rotating magnetic needle that responds to the earth’s magnetic poles by pointing North. - Lodestone (magnetite) – a natural magnet was used as the first compass on ships.

  5. Magnetic materials 3.Magnets (natural and man-made) are usually made up of ferromagnetic materials such as iron, nickel, cobalt and steel. - only strongly attracted to these ferromagnetic materials; has little or no attraction for other types of materials.

  6. Magnetic domains 4. Magnetic domains – groups of atoms that behave like tiny magnets. - If magnetized – domains line up in same direction - If un-magnetized – domains remain in a random arrangement * make drawings

  7. Unmagnetized Material Magnetized Material

  8. Permanent magnets • Permanent magnets – made by placing magnetic materials in a strong magnetic field causing a magnetic domains to line up. - most are made of iron/steel and a combination of other elements - Ex. Alnico – very strong permanent magnet - magnetism can be destroyed by heating, striking the magnet, and over long time periods

  9. Temporary magnets • Temporary magnets – are made up of magnetic materials but do not last a long time - by making contact with a magnet - by stroking the material in same direction with a permanent magnet - by using electricity (electromagnet)

  10. EQ3: What is electromagnetism and why is it so important? • Electromagnetism – the force created by the relationship and interaction between electricity and magnetism. • Contributions by two important scientists: 1. Hans Christen Oersted - 1820 - a Danish physicist who discovered that an electric field in his experiment set up a magnetic field and affected a nearby compass.

  11. Electromagnetism 2. Andre Marie Ampere – 1821 - a French physicist who discovered that coils or loops of conducting wire carrying current produces an even stronger magnetic field. - the more coils or loops, the stronger the magnetic field

  12. Electromagnetism • In 1825, scientists discovered the first electromagnet. • Electromagnet – a temporary magnet produced with a soft iron core material surrounded by coils or loops of wire(solenoid) that is controlled by electricity. - ways to increase the strength: 1) increase coils 2) increase current & 3) larger iron cores

  13. Uses of electromagnets • Many common and important uses of electromagnets: 1.Telephones 2. Doorbells 3. Stereo speakers 4. Pick up scrap metal (using a crane) 5. Electric motor*

  14. EQ5: How does the electric motor work? • Electric motor – a device that changes electrical energy into mechanical energy 1. The electromagnet is free to rotate between the poles of a permanent fixed magnet. 2. Electric current flowing around the coils of an electromagnet sets up a magnetic field. 3. Changing direction of current causes the poles to constantly reverse and rotate.

  15. Electric motors 4. The rotating electromagnet is connected to a shaft that turns parts or gears for motion. • Electric motors are found in many appliances and tools that have moving parts: Ex. Fans, mixers, washing machines, drills, saws, toys etc.

  16. EQ6. What is electromagnetic induction and why is it so important? • Electromagnetic induction (induced current) - the production of an electric current from a magnetic field. Two ways: • Moving a loop or coil of wire through a magnetic field. • Moving a magnet through a loop of wire.

  17. Electromagnetic induction • Contributions by two important scientists; 1. Michael Faraday – 1831 - an English scientist who discovered that an electric current could be caused by moving a wire through a magnetic field. 2. Joseph Henry – an American scientist made a similar discovery

  18. Electromagnetic induction • As a conducting wire cuts through the magnetic lines of force, it induces an electric current (Faraday’s law). • Galvanometer – instrument used to detect and measure very small amounts of electric current • The discovery of electromagnetic induction led to important inventions such as the electric generator and transformers.

  19. EQ7: How does the electric generator work? • Generator – a device that produces electricity from mechanical energy by rotating a coil of wire in a magnetic field. - the coil is rotated by an outside source of mechanical energy. - as the coils rotate within the magnetic field, an electric current flows through the coil.

  20. Generator - The coils of the electromagnets are connected to a turbine – large wheel with blades that rotates when pushed by water, steam or wind. - The direction of the coil changes twice with each revolution – producing alternating current (AC) • At power plants generators produce AC at a rate of 60 cycles/second or 60 Hz – changing direction 120 times/second.

  21. EQ8: How does a transformer work? • Transformer – a device that increases or decreases the voltage of AC. - made of two coils (primary and secondary) wrapped around the same iron core. - changes of current in the primary coil (incoming voltage) induces a change in the current in the secondary coil (outgoing voltage).

  22. Transformer • Two types of transformers: 1. Step-up transformer – the secondary coil has more loops or coils than the primary coil. - it increases the voltage - located at power plants and along the route at power substations to boost it up to travel long distances

  23. Transformer 2. Step-down transformer – the primary coil has more loops or coils than the secondary coil. - it decreases the voltage - located on utility poles (round bucket) and used for certain appliances and toys (trains). - can reduce very high voltage from power lines (750, 000 V) down to household use of 110 – 220 V of AC.

  24. Transformers

More Related