Chapter 8 Magnets

1. Chapter 8Magnets

2. BIG IDEA: A magnet is surrounded by a magnetic field that exerts a force on other magnets. Section 1: SCSh 1a-b, 3c, 3e-f, 4a, 9c, SPS 10c Section 2: SCSh 9c, SPS 10c Section 3: SCSh 9c, SPS 10b

3. All magnets have the following ___________ properties: • Magnets always have two opposite “_______,” called _________ and _______. • If _________, each part of a magnet has both north and south poles; we _______ see an unpaired north or south pole.

4. When near each other, ________ exert magnetic __________ on each other. • The __________ between magnets depend on the alignment of the poles; _______ unlike poles will ____________ each other and two like poles will ___________ each other. ____________________ Magnet ________________ Magnet Electromagnet

5. MAIN IDEA: ________________________________________________________________________________________________________________________________________________________________________________________________________

6. In _______, cobalt, nickel and a few other metals the atoms exert a _______ on the other atoms around them. Because of these forces, _______ groups of atoms align their magnetic poles so that almost all like poles point in the ________ direction. The groups of atoms with aligned magnetic poles are called magnetic ___________.

8. QUESTION? How do magnetic poles interact with each other? ANSWER: ________________________________________________________________________________________________________________________________________________________________________________________________

9. A _________ needle is a magnet that is free to _______ until it lines up in the north-south direction. The origin of the terms “________ pole” and “_______ pole” of a magnet come from the direction that a magnetized compass _______ points. The end of the magnet that pointed ________ was called the north pole of the magnet and the end that pointed ________ was called the south pole.

11. History of Magnetism First compass used: _______________ (in the twelfth century) Chinese sailors used a compass made of ________________ First magnetic metal found: ___________________(2500 yrs ago in current Turkey) Greeks called it “Lodestone” or “Magnesia” = _____________________

12. 3 Name three types of magnets: 1. _______________________________________ 2. _______________________________________ 3. _______________________________________ Two historic discovery places regarding magnets and their importance: 1. _______________________________________ 2. _______________________________________ 2 1 If a magnetic material were melted, would it continue to be magnetic, why? (hint: magnetic domain) 1. _______________________________________

13. The _________ force depended on the __________ and ___________ of the two magnets and also on the ____________ between them. The model of a magnetic ________ was developed to describe how a magnet exerts magnetic _______. • First, every ________ creates an energy field, called the magnetic ________, in the space around it. • Second, the _________ exerts _____ on any other magnet that is within its range.

14. QUESTION? What does the force between two magnets depend on? ANSWER:(Page 224) ____________________________________________________________________________________________________________________________________________________________________________________

15. Electromagnets = A ________ that is created by _______ current. This type of ______ is called an electromagnet. A single wire wrapped into a coil around a core is called a _______________.

16. KNOW: The more current would make an electromagnet stronger. 2 ways to increase the current. • apply more ________ = by adding a second battery. • add more _________ = of wire around the nail. The second method works because the ___________ in the electromagnet comes from the totalamount of current flowing around the _____. If there is 1 amp of _____ in the wire, each loop of wire adds 1 amp to the total amount that flows around the ______. Ten loops of 1 amp each make _____ total amps flowing around. By adding more turns, the same __________ is used over & over to get stronger _______________.

17. Wrap the _______ in many turns around the _____ and connect a ________. When current flows in the ______, the nail becomes a _________. To ______ north and south, reverse the connection to the ________, making the current flow the opposite ________.

18. Of course, nothing comes for free. By adding more __________ the resistance of the coil is also increased. _______________ the resistance makes the current a little ___________ & generates more __________. A good electromagnet is a ____________ between too much resistance and having enough _________ to get a strong enough __________.

19. The magnetic _______ exerted by an electromagnet depends on ____ factors: • The amount of electric ______ in the wire. • CURRENT ↑ then MAGNETIC FORCE ↑ • The amount of iron or steel in the electromagnet’s ____________. • METAL ↑ then MAGNETIC FORCE ↑ • The number of __________ in the solenoid. • COILS ↑ then MAGNETIC FORCE ↑

20. Electric motors convert ________ energy into mechanical energy. Permanent magnets and electromagnets can work together to make _________ motors and generators. The secret is in the ability of an electromagnet to ________ from north to south. By changing the __________ of electric current, the electromagnet changes from attract to repel, and spins the ____________.

21. QUESTION?Why is it necessary to continually reverse the direction of the current flow in the coil of an electric motor? ANSWER: (page 236-237) When the end of the coil move past a pole of the permanent magnet, reversing the current causes the end of the coil to be attracted to the other (next) pole of the permanent magnet.

22. All electric _________ must have ________ things to work: • A rotating element (_________) with magnets. • A stationary ___________ that surrounds the rotor. • A ______________ that switches the electromagnets from north to south at the right place to keep the rotor spinning. The electromagnet must switch from north to south as each ________ magnet passes by to keep the rotor turning. The switch that makes this happen is called a __________________.

23. Both electrical _______ and magnetic _________exist between electric charges. Scientists now believe both forces are ______ aspects of _______ force, the electromagnetic _______________. A _________ through a wire creates a magnet. The reverse is also true: If a _________ is moved through a coil of wire, then electric ______________ is created. This _________ is called electromagnetic induction because a moving magnet induceselectric ____________ to flow.

24. MAIN IDEA: ________________________________________________________________________________________________________________________________________________________________________________________________________.

25. When a _________ moves into a coil of wire, it induces electric current to flow in the ________. The current ________ if the magnet ________ moving. If the magnet is pulled back _______ again, the current flows in the opposite direction. A changing magnetic ____________ is what makes the electricity flow.

26. Electromagnetic _____________ enables us to transform mechanical energy (moving magnets) into __________ energy. Any machine that causes magnets to move past wire coils generates electric currents. These machines include giant electric __________ plants and computer ________ drives. Power plants use electromagnetic induction to create _________. A generator is a combination of mechanical and electrical systems that converts _________ energy into electrical ____________.

27. A power plant____________contains a turbine that turns magnets inside loops of _________, generating electricity.

28. In the top sketch the north pole on the disk induces a south pole in the _________________, causing current to flow one way. When the disk rotates, the ____________ in the coil is reversed, and the electric current generated also reverses. THIS IS ALTERNATING CURRENT (_____)

29. 3 Name three things a motor requires: 1. _______________________________________ 2. _______________________________________ 3. _______________________________________ Two forces combine to produce electromagnetic forces: 1. _______________________________________ 2. _______________________________________ 2 1 How does electromagnetic induction generate electricity (AC) 1. _______________________________________

30. Explain how a magnet exerts a force. ____________________________________________________________________________________________________

31. Describe the magnetic field produced by an electric current. _________________________________________________________________________________________________________

32. Explain how a electromagnet produced a magnetic field. __________________________________________________________________________________________________________________________________________

33. Explain how an electric motor operates. __________________________________________________________________________________________________________________________________________

34. Describe how a generator produces an electric current. __________________________________________________________________________________________________________________________________________