1. Static Electricity What are the fundamental particles and how do they interact?

2. Atomic Structure Electrons are lighter and are much easier to remove from an atom. Electrons are lighter and are much easier to remove from an atom. Atoms are electrically neutral Atoms are electrically neutral Ions: atoms have lost one or more e- Ions: atoms have lost one or more e- Lithium charges 3 electrons (-3) 3 protons(+3) 3 neutrons(0)

3. 3 Big Rules of Electrostatics Opposites Attract Likes Repel Only Electrons Move

4. How do objects pick up static charge? Friction causes electrons to transfer to a material with more “affinity”. Friction causes electrons to transfer to a material with more “affinity”. Conservation of charge: Total charge remains the same. Conservation of charge: Total charge remains the same.

5. Electron Affinity Cellophane tape Rubber Copper, brass Amber Wood Cotton Silk Wool Nylon Glass Rabbit fur Becomes more Negative

6. Electrostatic Forces Experiments with pith balls Experiments with pith balls

7. Does a charged object attract a neutral object? A neutral stream of water bends toward the negatively charged comb A neutral stream of water bends toward the negatively charged comb

8. Polarization of Charges Charges inside an object separate and attraction is then possible. Charges inside an object separate and attraction is then possible.

9. Charge Transfer Conductors: materials that allow charges move easily. Static charges spread out evenly on the surface and transfer easily. Conductors: materials that allow charges move easily. Static charges spread out evenly on the surface and transfer easily. ex: Metals, Ion solutions Insulators: Materials that do not allow charge to flow easily. ex: air, wood, plastic to flow easily. ex: air, wood, plastic

10. If an object is charged will it remain charged forever? Static shocks (lightning) Static shocks (lightning) Water molecules (polar molecules) touch and remove charges. Water molecules (polar molecules) touch and remove charges. Large round surfaces can hold more charge. Large round surfaces can hold more charge.

11. Charge Transfer Two identical conducting spheres are charged and then allowed to touch. before contact What is the net charge for both? Which way will the charge flow?

12. After contact they share the charge. After contact they share the charge. Describe the charge transfer. Describe the charge transfer.

13. Metal sphere A has a charge of +12 elementary charges and identical sphere B has a charge of +16 elementary charges. After the two spheres are brought into contact, the charge on sphere A is A B A B a)+28 elem. charges c)+2 elem. Charges b)-2 elem. charges d)+14 elem. charges +12 +16

14. What if the spheres are not the same size? What if one sphere was the earth?

15. Grounding when an object is connected to the earth it becomes neutral. when an object is connected to the earth it becomes neutral. Earth can absorb any amount of excess e- or supply any amount of e- to make an object neutral. Earth can absorb any amount of excess e- or supply any amount of e- to make an object neutral. Symbol for ground: Symbol for ground:

16. Electric Force Electric forces must be strong because they can easily produce accelerations larger than the acceleration caused by gravity. Electric forces must be strong because they can easily produce accelerations larger than the acceleration caused by gravity. These forces can be either repulsive or attractive and so are either positive or negative (respectively) These forces can be either repulsive or attractive and so are either positive or negative (respectively) Charges exert forces on other charges at a distance Charges exert forces on other charges at a distance The force is stronger when the charges are closer together The force is stronger when the charges are closer together Like charges repel; opposite charges attract Like charges repel; opposite charges attract

17. Forces on Charged Bodies An electroscope is a device consisting of a metal knob connected by a metal stem to two thin, lightweight pieces of metal foil, called leaves An electroscope is a device consisting of a metal knob connected by a metal stem to two thin, lightweight pieces of metal foil, called leaves

18. Charging by Conduction When a negatively charged rod is touched to the knob of an electroscope, electrons are added to the knob and then spread all over the metal surfaces. When a negatively charged rod is touched to the knob of an electroscope, electrons are added to the knob and then spread all over the metal surfaces. Thus the two leaves are negatively charged and repel each other Thus the two leaves are negatively charged and repel each other The electroscope has been given a net charge The electroscope has been given a net charge The same thing happens if the electroscope is charged positively The same thing happens if the electroscope is charged positively Charging a neutral body by touching it with a charged body is called charging by conduction Charging a neutral body by touching it with a charged body is called charging by conduction

19. Charging by Conduction

20. Separation of Charge on Neutral Objects If you bring a charged rod near a neutral electroscope, you can make the electroscope behave as if it were charged while it is still electrically neutral by causing the interior charges to separate If you bring a charged rod near a neutral electroscope, you can make the electroscope behave as if it were charged while it is still electrically neutral by causing the interior charges to separate

21. Charging by Induction However, if after you cause the interior charges to separate, you give the repelled charges a way out of the object, then you can permanently charge the object However, if after you cause the interior charges to separate, you give the repelled charges a way out of the object, then you can permanently charge the object This process of charging an object without touching it is called charging by induction This process of charging an object without touching it is called charging by induction

22. Charging by Induction

24. Coulomb’s Law Coulomb’s Law, also known as the Electrostatic Law, states that the force between two charged objects can be found by: Coulomb’s Law, also known as the Electrostatic Law, states that the force between two charged objects can be found by: K is Coulomb’s constant (also called the Electrostatic Constant) and has a value of 8.99x10 9 Nm 2 /C 2 q 1 is the charge of one charged object q 2 is the charge of the other charged object r is the distance between the two charges Units for the charges are in coulombs (C) Unit for the distance is meters (m) Unit for the electrostatic force are in newtons (N)

25. Elementary Charge An elementary charge is the magnitude of the charge of an electron An elementary charge is the magnitude of the charge of an electron The charge on a single electron is 1.60x10 -19 C The charge on a single electron is 1.60x10 -19 C One coulomb is the charge of 6.24x10 18 electrons or protons One coulomb is the charge of 6.24x10 18 electrons or protons A typical lightning bold can carry 5C to 25C of charge A typical lightning bold can carry 5C to 25C of charge

26. Find the Electrostatic Force between these two point charges.

27. Electric Field An electric field is a region in space where a force is exerted on a positive test charge An electric field is a region in space where a force is exerted on a positive test charge Electric lines of force (Electric Field Lines) represent the direction that a positive test charge would move in an electric field Electric lines of force (Electric Field Lines) represent the direction that a positive test charge would move in an electric field By convention, they start at positively charged objects and end at negatively charged objects By convention, they start at positively charged objects and end at negatively charged objects

28. Electric Field Lines

29. Top: 2 positive charges repel from one another Bottom: 1 positive charge emits an electric field force towards a negative charge 3-Dimensional Image of repulsive electronic forces

30. A charge in an electric field experiences an electric force A charge in an electric field experiences an electric force The equation to find the strength of this electric force upon a test charge within the electric field is: The equation to find the strength of this electric force upon a test charge within the electric field is: E = F/q This states that the electric field strength (in units of N/C) is a measure of the force upon a test charge divided by the charge value of the test charge This states that the electric field strength (in units of N/C) is a measure of the force upon a test charge divided by the charge value of the test charge Electric Field Strengths are vector quantities, which means that they have both a magnitude as well as a direction Electric Field Strengths are vector quantities, which means that they have both a magnitude as well as a direction

31. Question What is the electric field strength of a 5.8µC test charge that is experiencing a repulsive force of 138N? What is the electric field strength of a 5.8µC test charge that is experiencing a repulsive force of 138N? Remember that 1µC = 1x10 -6 C Remember that 1µC = 1x10 -6 C Note that the force upon the test charge is repulsive… What sign convention should it follow? Note that the force upon the test charge is repulsive… What sign convention should it follow?

32. Question At which point is the electric field strength the greatest? (A, B, or C) At which point is the electric field strength the greatest? (A, B, or C)

33. Is it possible to store charge? Ans: give an e- what it wants. To be near + charges. Ans: give an e- what it wants. To be near + charges. The capacitor: Two plates separated but very close. Each has an opposite charge. The capacitor: Two plates separated but very close. Each has an opposite charge.

34. Capacitor

36. This is why you shouldn’t use your cell phone while driving. Your cell phone gives off electrons in its signal This gives the phone a positive charge which attracts the negative charge of the lighning bolt

37. Electric Potential Difference Work is done by the electric field if the electric force acting on the charge causes it to move from one point to another Work is done by the electric field if the electric force acting on the charge causes it to move from one point to another These two points differ in their electric potential These two points differ in their electric potential The magnitude of the work done on the charge by the electric field is a measure of the difference in potential The magnitude of the work done on the charge by the electric field is a measure of the difference in potential

38. The Electric Potential Difference is the work done per unit charge as a charge is moved between two points in an electric field The Electric Potential Difference is the work done per unit charge as a charge is moved between two points in an electric field This follows the mathematical equation: This follows the mathematical equation: V = W/q = (Fd)/q Where V is the electric potential difference, W is the amount of work done, and q is the charge that is moved Unit for the electric potential difference is the volt (V) Unit for the electric potential difference is the volt (V)

39. Question What is the electric potential difference if a 100N force moves a 6µC charge a distance of 5cm? What is the electric potential difference if a 100N force moves a 6µC charge a distance of 5cm?