Electric Charge and Electric Force

1. Electric Charge and Electric Force

2. Matter is made up of atoms. Atoms are made up of Electrons Protons Neutrons

3. ATOM Electrons are negatively charged Protons are positively charged Neutrons have no charge

4. A non moving accumulation of net charge is called static charge. Electrostatics is the study of electrical charges that can be collected and held in place.

5. OBJECTS CAN BE: Conductors Insulators Semi-Conductors Super Conductors

6. CONDUCTORS Conductors are materials that electric charge can move through easily. Their outer (valence) electrons are “loose”. Ex: copper, silver & earth

7. An object connected to the Earth, or the ground, by a good conductor, is said to be grounded.

8. INSULATORS Insulators are objects that don’t allow electrons to move through them easily. Their valence electrons are tightly held. Ex: plastic, wood, rubber & glass

9. SEMICONDUCTORS Semiconductors are materials that behave as insulators or conductors. Their valence electrons are tightly held until given a small energy boost. Ex: silicon, germanium

10. SUPERCONDUCTORS Some materials become superconductors below their critical temperature (near 0 Kelvin – absolute zero). They have zero resistance to charge movement.

11. ELECTRIC CHARGE IS AN ELECTRICAL PROPERTY THAT CREATES A FORCE BETWEEN OBJECTS. • POSITIVE • NEGATIVE • NO CHARGE (NEUTRAL)

12. POSITIVE when it has more protons NEGATIVE when it has more electrons NEUTRAL when it has same number of protons and electrons (no charge) AN OBJECT IS

13. ELECTRIC CHARGE Is measured in Coulombs (C) Electron Charge=-1.6 x 10-19C Proton Charge=+1.6 x 10-19C

14. ELECTRIC CHARGE +1.0 coulomb of charge equals 6.25 x 1018 protons -1.0 coulomb of charge equals 6.25 x 1018 electrons

15. CHARACTERISTICS OF ELECTRIC CHARGE 1. There are three kinds of charges - positive, negative, and neutral 2. Like charges repel each other and unlike charges attract each other.

16. Like charges repel

17. Unlike charges attract

18. CHARACTERISTICS OF ELECTRIC CHARGE 3. Charges have a natural tendency to be transferred between unlike materials. 4. Electrical charges are always conserved.

19. Charges are quantized. If an object is charged, its charge is always a multiple of a fundamental unit charge 1.6 x 10-19 C. CHARACTERISTICS OF ELECTRIC CHARGE

20. 6. The SI unit of charge is Coulomb (C). 7. Objects can be charged by friction, contact, polarization and induction. CHARACTERISTICS OF ELECTRIC CHARGE

21. CHARGING OBJECTS Protons and neutrons are relatively fixed in the nucleus, but the outermost electrons in some atoms can be easily transferred from one atom to another

22. CHARGING OBJECTS Objects gaining electrons are negatively charged Objects losing electrons are positively charged

23. EARTH Is an infinite reservoir of electrons. It can accept and supply an unlimited number of electrons.

24. When a conductor is connected to Earth by means of a conducting wire or copper pipe, it is said to be grounded. Ex: plumbing fixtures, metal faucets, sinks & pipes.

25. CHARGING METHODS • Friction • Contact • Induction • Polarization

26. FRICTION Electrons can transfer from one material to another when they are rubbed against each other.

27. Rubbing glass rod with silk Silk will gain electrons and glass rod will lose electrons. Glasspositively charged Silknegatively charged

28. Rubbing rubber with fur Rubber will gain electrons and fur will lose electrons. Furpositively charged Rubbernegatively charged

30. CONTACT Electrons can transfer from one material to another when the two materials touch.

31. INDUCTION Is the process of charging an object by grounding it while it is near another charged object. When an object is charged by induction, its charge is opposite to that of the charging object.

32. INDUCTION

33. Induction

34. POLARIZATION In insulators, the presence of a charged object, results in more positive charge on one side of the molecule than the other.

35. POLARIZATION Insulator

36. POLARIZATION The rearrangement of charges within individual molecules produces an induced charge on the surface of the insulators. This effect is known as polarization.

37. ELECTROSCOPE Is a device used to detect the presence of electrical charges.

38. ELECTROSCOPE http://www.shep.net/resources/curricular/physics/P30/Unit2/electroscope.html

39. LIGHTNING A lightning bolt occurs when billions of electrons are transferred at the same time. Lightning bolts also occur between the negative area of one cloud and a positive area of another cloud.

40. LIGHTNING

41. LIGHTNING

42. LIGHTNING Lightning is a large discharge of static electricity. The friction from the movement of water droplets in the cloud can build up areas of positive and negative charge.

43. LIGHTNING The negative and positive charges repel each other so the top of the cloud is positive and the bottom of the cloud is negative.

44. LIGHTNING The negative charge at the bottom of the cloud causes a positive charge to be induced on the Earth’s surface.

45. LIGHTNING When the charge difference is great enough, the air becomes a conductor, the electrons in the cloud are transferred to the positively charged ground.

46. LIGHTNING Benjamin Franklin experimented with electricity. He discovered that sparks leave a sharply pointed object more readily than a rounded object.

47. He invented the lightning rod. It is a pointed rod that is attached at the top of a building and connected to the ground by a cable. It prevents a large build up of charge on the building.

48. Note: Lightning tends to strike the highest point nearby so beware during a storm.

50. COULOMB’S LAW Coulomb’s law states that for charged particles the distance between the charges varies directly with the product of the two charges and inversely with the square of the distance between them.