Física y química 3º E.S.O.

1. Física y química 3º E.S.O. Unit 5: Electricity and magnetism U_5_2_I_Methods of charging in contact U.5_2 d1

2. Bloque 4. El movimiento y las fuerzas. 4.1. Las fuerzas. Efectos de las fuerzas. 4.2. Fuerzas de especial interés: peso, normal, rozamiento, fuerza elástica. 4.3. Principales fuerzas de la naturaleza: gravitatoria, eléctrica y magnética. Criterios de evaluación C.E.4.8. Conocerlos tipos de cargas eléctricas, su papel en la constitución de la materia y las características de las fuerzasque se manifiestan entre ellas. . Estándares de aprendizaje evaluables E.A.4.8.1. Explica la relación existente entre las cargas eléctricas y la constitución de la materia y asocia la carga eléctrica de los cuerpos con un exceso o defecto de electrones. E.A.4.8.2. Relaciona cualitativamente la fuerza eléctrica que existe entre dos cuerpos con su carga y la distancia que los separa, y establece analogías y diferencias entre las fuerzas gravitatoria y eléctrica. Criterios de evaluación C.E.4.9. Interpretar fenómenos eléctricos mediante el modelode cargaeléctricay valorar la importanciade la electricidaden la vida cotidiana. Estándares de aprendizaje evaluables E.A.4.9.1. Justifica razonadamente situaciones cotidianas en las que se pongan de manifiesto fenómenos relacionados con la electricidad estática. Criterios de evaluación C.E.4.10. Justificar cualitativamentefenómenos magnéticos y valorarla contribución del magnetismo en el desarrollo tecnológico. . Estándares de aprendizaje evaluables E.A.4.10.1. Reconoce fenómenos magnéticos identificando el imán como fuente natural del magnetismo y describe su acción sobre distintos tipos de sustancias magnéticas. E.A.4.10.2. Construye, y describe el procedimiento seguido pare ello, una brújula elemental para localizar el norte utilizando el campo magnético terrestre. Criterios de evaluación C.E.4.11. Comparar los distintostiposde imanes, analizar su comportamiento y deducir medianteexperienciaslas característicasde lasfuerzas magnéticas puestas de manifiesto, asícomosurelación conla corriente eléctrica. Estándares de aprendizaje evaluables E.A.4.11.1. Comprueba y establece la relación entre el paso de corriente eléctrica y el magnetismo, construyendo un electroimán. E.A.4.11.2. Reproduce los experimentos de Oersted y de Faraday, en el laboratorio o mediante simuladores virtuales, deduciendo que la electricidad y el magnetismo son dos manifestaciones de un mismo fenómeno. U.5_2 d2

3. 5.2.1. Structure of an atom and charge Structure of an atom U.5_2 d3

4. 5.2.1. Structure of an atom and charge A positive ion is an atom with one or more electrons removed A neutral atom has the same number of protons as electrons A negative ion has gained one or more electrons U.5_2 d5

5. 5.2.1. Structure of an atom and charge U.5_2 d4

6. 5.2.1. Structure of an atom and charge Classify these two examples as a neutral atom, a positive ion or a negative ion A neutral atom has the same number of protons as electrons A positive ion is an atom with one or more electrons removed A negative ion has gained one or more electrons U.5_2 d6

7. 5.2.1. Structure of an atom and charge A positive ion is an atom with one or more electrons removed A neutral atom has the same number of protons as electrons A negative ion has gained one or more electrons U.5_2 d7

8. 5.2.2. Static electricity (Revision) An object whose atoms lose electrons becomes positively charged An object whose atoms gain electrons becomes negatively charged The electrons contained within the objects are prone to move or migrate to other objects. U.5_2 d8

9. 5.2.2. Static electricity (Revision) The buildup of unbalanced electric charges on an object is called “static electricity” When electric charges on an object are unbalanced there is static electricity U.5_2 d9

10. 5.2.3. Law of conservation of charge (Rev.) Is new electrical charge created or destroyed? Neither protons nor electrons in an object can be created or destroyed An object becomes charged when electric charges move from one place to another. Electrons can be transferred from one object to another, but there aren´t new electrons. The law of conservation of charge states that in a closed system, the total amount of charge is conserved since charge can neither be created nor destroyed. U.5_2 d10

11. 5.2.4. Conductors and insolators U.5_2 d11

12. 5.2.4. Conductors and insolators U.5_2 d12

13. 5.2.4. Conductors and insolators A semiconductor has a few free electrons and atoms with bound electrons that act as insulators. U.5_2 d13

14. 5.2.5. Methods of Charging At distance In contact By friction By conduction By induction U.5_2 d14

15. 5.2.5.1. Methods of Charging (In contact, by friction) When two different non-conducting materials are rubbed, electrons are transferred between the two materials being rubbed In contact By friction Rubber Rubber Fur Fur When insulators are charged by rubbing, only the rubbed area becomes charged. There is no tendency for the charge to move into other regions of the material. This is what causes static electricity. U.5_2 d15

16. 5.2.5.1. Methods of Charging (In contact, by friction) When you give your hair a quick comb two different insulating materials are being rubbed and electrons in your hair are transferred to the hair comb. U.5_2 d16

17. 5.2.5.1. Methods of Charging (In contact, by friction) U.5_2 d17

18. 5.2.5.1. Methods of Charging (In contact, by friction) The atoms that make up all substances have different forces of attraction for their electrons. The atoms of the comb hold on their electrons more tightly than the atoms of your hair. The friction causes electrons to gain energy. Electrons gain enough energy to leave the atoms of your hair and they pass to the comb atoms. U.5_2 d18

19. 5.2.5.1. Methods of Charging (In contact, by friction) Electrons gain enough energy to leave the atoms of your hair and they pass to the comb atoms. - The comb has gained electrons, giving it a negative charge. - The hair has lost electrons, giving it a positive charge. U.5_2 d19

20. Rubber Fur The atoms that make up all substances have different forces of attraction for their electrons. Rubber Fur Rubber Fur U.5_2 d20

21. Rubber Fur Friction causes electrons to gain energy. Electrons gain enough energy to leave the atoms of the fur and pass to the rubber atoms. Friction Electron transfer Rubber Fur Rubber Fur U.5_2 d21

22. - The atoms in the rabber have gained electrons, giving it a negative charge. - The atoms in the fur have lost electrons, giving it a positive charge. Rubber Fur Negative Positive Rubber Fur Rubber Fur U.5_2 d22

23. 5.2.5.1. Methods of Charging (In contact, by friction) As you move further down the list, the materials increase in their tendency to gain extra electrons and become negatively charged. A list showing the relative attraction of different substances for electrons is shown. This list is called the Electrostatic series or Triboelectric series. U.5_2 d23

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25. 5.2.5.1. Methods of Charging (In contact, by friction) U.5_2 d25

26. 5.2.5.1. Methods of Charging (In contact, by friction) Decide what will be the final distribution of charges when an amber rod is rubbed with fur. Explain your answer. U.5_2 d26

27. 5.2.5.1. Methods of Charging (In contact, by friction) Amber is further down in the electrostatic series than fur. The atoms in the amber rod hold on their electrons more tightly than the atoms in the fur. The friction causes electrons to gain energy. U.5_2 d27

28. 5.2.5.1. Methods of Charging (In contact, by friction) Electrons gain enough energy to leave the atoms of the fur, so that they pass to the rod. - The amber rod gains extra electrons and becomes negatively charged. - The fur loses electrons and becomes positively charged. U.5_2 d28

29. 5.2.5.2. Methods of Charging (In contact, by conduction) At distance In contact By friction By conduction By induction U.5_2 d29

30. 5.2.5.2. Methods of Charging (In contact, by conduction) When a charged object is placed in contact with a conductor, electrons move from one object to another. Charged object Conductor sphere U.5_2 d30

31. 5.2.5.2. Methods of Charging (In contact, by conduction) When a charged object is placed in contact with a conductor, electrons move from one object to another. A charged object (the rod) is getting closer to another object (the conducting sphere). U.5_2 d31

32. 5.2.5.2. Methods of Charging (In contact, by conduction) When a charged object is placed in contact with a conductor, electrons move from one object to another. When the charged object (the rod) is placed in contact with the other object (the sphere), some electrons on the rod can move to the sphere U.5_2 d32

33. 5.2.5.2. Methods of Charging (In contact, by conduction) When a charged object is placed in contact with a conductor, electrons move from one object to another. Both the rod and the sphere are charged with an excess of electrons. Only the charge in excess is shown. U.5_2 d33

34. 5.2.5.2. Methods of Charging (In contact, by conduction) When a charged object is placed in contact with a conductor, electrons move from one object to another. When the rod is removed, the sphere is left with a charge. The object being charged is always left with a charge having the same sign as the object doing the charging U.5_2 d34

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36. 5.2.5.2. Methods of Charging (In contact, by conduction) Charging by Conduction: Charging an object by contact with another charged object. At the end, both objects have the same type of charge. Electroscope U.5_2 d36

37. 5.2.5.2. Methods of Charging (In contact, by conduction) Charging by Conduction: Negative object touches a neutral object Remember: In solids, only electrons move Finally, both objects have the same type of charge. U.5_2 d37

38. 5.2.5.2. Methods of Charging (In contact, by conduction) Charging by Conduction: Positive object touches a neutral object Remember: In solids, only electrons move Finally, both objects have the same type of charge. U.5_2 d38

39. 5.2.5.2. Methods of Charging (In contact, by conduction) If a conductor carries excess charge, the excess is distributed over the surface of the conductor. Faraday cage U.5_2 d39

40. 5.2.5.2. Methods of Charging (In contact, by conduction) Faraday cage: If a cage is made of metal, anything inside the cage is shielded from outside electricity U.5_2 d40

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