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General science unit 3 electricity and magnetism
- 1. General Science Unit 3: Electricity and Magnetism Chapter 7
- 2. 7.1 Standards and Objectives Identify and describe the properties of magnets. • 6.S.1A.3 • 6.S.1B.1 Identify and describe Explain how magnetic poles interact. • 6.S.1A.3 Explain Develop and use models to exemplify how magnetic fields produced by electrical energy flow in a circuit is interrelated in electromagnets, generators, and simple electrical motors. • 6.P.3A.4 Develop and use
- 3. 7.1 Untamed Science Video Magnetism: What’s the Attraction? https://classroom.google.com/c/ODU5NjI2NzA2MFpa/a/NTc3MjYwOD ExMlpa/details
- 4. 7.1 What is Magnetism? In short, magnetism is the attraction or repulsion of magnetic materials. Any material that attracts iron and materials that contain iron is considered a magnet.
- 10. Questions to consider • What are some properties of magnets? • Contain iron • Has two poles • Is attracted to other objects that contain iron. • How do magnetic poles interact? • If poles are the same, they repel • If poles are different, they attract • Magnetic pole interactions cause a magnetic field
- 11. 7.2 Standards and Objectives Describe a magnetic field. 6.S.1A.2 6.S.1A.3 6.S.1A.6 Describe Earth’s magnetic field. 6.S.1A.2 6.S.1A.4
- 13. Page 272 What is Earth’s magnetic field like? • Earth has two poles and a magnetic field around just like a bar magnet. • The magnetic field is generated from circulation of the liquid iron core. • The magnetic field is similar to that of a bar magnet.
- 14. Magnetic declination • In layman’s terms, it is the difference between the location of the physical north pole and the magnetic north pole of the earth.
- 18. 7.3 Standards and Objectives Explain how electric current is related to magnetism. •6.S.1A.3 •6.P.3A.4Explain Identify some characteristics of a magnetic field produced by a current. •6.P.3A.4 •6.S.1A.2 •6.S.1A.6 Identify Describe the characteristics of solenoids and electromagnets. •6.P.3A.4 •6.S.1A.2 •6.S.1A.6 Describe
- 19. Things to ponder… • How are electric currents and magnetic fields related? • What is a magnetic field produced by a current like? • What are the characteristics of solenoids and electromagnets?
- 20. Hans Christian Oersted • In 1820, he accidentally discovered that a magnetic field could be produced by an electric current. • He was a professor at the University of Copenhagen
- 22. Compass Deflection Page 275 • From the video, what happened to the compasses when the electric current was removed? • What about when the electric current was on? • Explain the movement of the compass needles during the experiment.
- 24. What is a magnetic field produced by a current is like? The magnetic field produced by a current has a strength and direction. The field can be turned on and off, have it’s direction reversed, or have its strength changed. Page 277
- 28. Oersted’s Experiment • What did Oersted conclude? He concluded that an electric current does create a magnetic field around the wire and in the direction of the current flow.
- 29. How does a current affect a compass? The moving current deflects the compass needle based on its direction of flow.
- 31. How do we change the strength of an electromagnet? • Increase the electric current • Increase the number of turns in the wire carrying the electric current. Page 277
- 32. Poles of a solenoid • How do we change the magnetic poles of a solenoid? We change the magnetic poles by changing the direction of current flow. Page 278
- 33. 7.4 Standards and Objectives • 6.P.3A.4 • Explain how electrical energy can be transformed into mechanical energy. • Describe how galvanometers work. • Describe how electric motors work.
- 34. How is electrical energy transformed into mechanical energy? • Electrical energy is transformed into mechanical energy through devices called electric motors. • Electric motors work on the principle of when a wire with a current is placed in a magnetic field, electrical energy is transformed into mechanical energy. • Electric Motor Animation https://youtu.be/Xi7o8cMPI0E Page 281
- 35. Electric Motors • They operate by rotating a wire with an electric current within a permanent magnetic field. • The wire generates a magnetic field that tries to align with the magnetic poles of the permanent magnet. • A small switch called a commutator turns the current on and off preventing the alignment of the magnetic field with the permanent magnetic poles. Page 284
- 36. Electric motor detailed operation • https://youtu.be/wxG3cwugXgs
- 37. Galvanometer? What is this? • Galvanometers are devices that measure small currents. • They can be found in instruments like • Automotive fuel gauges • Volt meters • Car speedometer Page 282
- 38. Galvanometer operation principle • Galvanometers operate on the principle of a suspended electromagnet coil placed between opposite poles of a permanent magnet. • When a current is run into the electromagnetic coil, the magnetic field created attempts to align with the poles of the permanent magnet. • The coil has a pointer attached, which is used to indicate a specific purpose. (Amount of current going to the car’s battery) Page 282
- 40. 7.5 Standards and Objectives • 6.P.3A.4 • Explain how an electric current can be produced in a conductor. • Describe how a generator works. • Describe what a transformer does. • Describe the similarities of motors and generators.
- 41. Electric current induction • If a wire coil is moved through a magnetic field, a electric current is generated within the wire. • If a permanent magnet is moved through a wire coil, an electric current is generated within the wire. • Page 284, 288
- 42. Two types of electric current • Direct Current (DC) • The charges of the current flow in one direction. • The charges move from one end of a battery to the other end. • Alternating Current (AC) • The charges in the current rapidly change directions • This current if generated by either moving the coil or the magnet up and down repeatedly. • The major advantage of AC over DC is that AC voltage can be easily raised or lowered. • Page 289
- 43. Generators • Generators function by rotating a coil of wire within a magnetic field to produce a current. • Generators use motion (mechanical energy) in a magnetic field to produce current. • They can be: • Hand driven • Water driven • Wind powered Page 290
- 44. Transformers • Transformers are devices that increase or decrease voltage. • They are found on light poles, in cell phones, on electric power cables, etc. • There are two types: • Step up • Step down • Page 292
- 47. Ratio • The ratio of the number of turns on the primary winding side to the secondary winding side determines what happens to the current. • Primary winding = 5 turns • Secondary winding = 10 turns The result is a doubling of the electric current voltage. 10 ÷ 5 = 2
- 48. Chapter test on Wednesday Take textbooks and notes home to study. Bonus points on the test will be added through a random process. 20 Multiple Choice Questions