1. Electrical Charges
Physics A
Static #1

2. Learning Targets
I can describe the characteristics (charge, location, ability to move) of subatomic particles.
I can calculate the charge of an object using the charge of one electron and the number of electrons that the object is deficient or has in excess.
I can determine whether an object is positively or negatively charged when given the number of protons and electrons in/on the object.

3. Static Electricity & the Everyday World
What are some examples of static electricity that you witness on a regular basis?
Describe the forces associated with static electricity.
Why are electrostatic forces important to the everyday world?
How can an object be charged and what affect does that charge have upon other objects in its vicinity?

4. Structure of Matter All material objects are composed of atoms.
There are different kinds of atoms known as elements; these elements can combine to form compounds.
Different compounds have distinctly different properties.
Material objects are composed of atoms and molecules of these elements and compounds, thus providing different materials with different electrical properties.

5. Structure of Matter
An atom consists of a nucleus and a vast region of space outside the nucleus.
Electrons are present in the region of space outside the nucleus.
They are negatively charged and weakly bound to the atom.
Electrons are often removed from and added to an atom by normal everyday occurrences.

6. Structure of Matter
The nucleus of the atom contains positively charged protons and neutral neutrons.
These protons and neutrons are not removable by usual everyday methods.
Electrostatic phenomenon can never be explained by the movement of protons.

7. Summary of Subatomic Particles
Proton
Neutron
Electron
Location
Bound
(weakly or tightly)
Charge
Mass

8. Summary of Subatomic Particles
Proton
Neutron
Electron
Location
IN nucleus
OUTSIDE nucleus
Bound
(weakly or tightly)
TIGHTLY bound
WEAKLY bound
Charge
POSITIVE charge
NO charge
NEGATIVE charge
Mass
MASSIVE
NOT massive

9. Electron Affinity
The presence of different atoms in objects provides different objects with different electrical properties.
Electron Affinity: the relative amount of attraction that a material has for electrons
If atoms of a material have a high electron affinity, then that material will have a relatively high attraction to electrons.

10. Neutral vs. Charged Objects
A proton and an electron have an equal amount but an opposite type of charge.
If an atom contains equal numbers of protons and electrons, the atom is described as being electrically neutral.
If an atom has an unequal number of protons and electrons, then the atom is electrically charged.
Any particle that contains less electrons than protons is said to be positively charged.
Any particle that contains more electrons than protons is said to be negatively charged.

11. Neutral vs. Charged Objects
Positively Charged
Negatively Charged
Uncharged

12. Charge as a Quantity The charge of an object is a measurable quantity.
The charge possessed by an object is expressed using the unit known as the Coulomb (C).
One Coulomb of charge is an abnormally large quantity of charge, the units of microCoulombs (µC) or nanoCoulombs (nC) are more commonly used as the unit of measurement of charge.

13. Charge as a Quantity
The charge on a single electron is -1.6 x Coulomb.
What is the charge on a single proton?
The quantity of charge on an object reflects the amount of imbalance between electrons and protons on that object.

14. Charge as a Quantity
In conclusion, an electrically neutral object is an object that has a balance of protons and electrons.
In contrast, a charged object has an imbalance of protons and electrons.

15. ____ are the charged parts of an atom.
a. Only electrons b. Only protons c. Neutrons only d. Electrons and neutrons e. Electrons and protons f. Protons and neutrons

16. TRUE or FALSE: An object that is positively charged contains all protons and no electrons.

17. TRUE or FALSE: An object that is negatively charged could contain only electrons with no accompanying protons.

18. TRUE or FALSE: An object that is electrically neutral contains only neutrons.

19. Identify the following particles as being charged or uncharged
Identify the following particles as being charged or uncharged. If charged, indicate whether they are charged positively or negatively.

20. Identify the following particles as being charged or uncharged
Identify the following particles as being charged or uncharged. If charged, indicate whether they are charged positively or negatively.

21. Consider the graphic below of a neutral oxygen atom.
Explain what must happen in order for the oxygen atom to become negatively charged.

22. Consider the graphic below of a neutral oxygen atom.
Explain what must happen in order for the oxygen atom to become positively charged.

23. Determine the quantity and type of charge on an object that has 3
Determine the quantity and type of charge on an object that has 3.62 x 1012 more protons than electrons.

24. Determine the quantity and type of charge on an object that has 4
Determine the quantity and type of charge on an object that has 4.51 x 105 more electrons than protons.

25. After some rather exhausting counting, a physics teacher determines that a very small sample of an object contains x 1017 protons and 5.26 x 1014 electrons; the charge on this object is ____ Coulombs.

26. After some rather exhausting counting, a physics teacher determines that a very small sample of an object contains x 1014 protons and x 1016 electrons; the charge on this object is ____ C.

27. The amount of charge carried by a lightning bolt is estimated at 10 Coulombs. What quantity of excess electrons is carried by the lightning bolt?

28. Learning Targets
I can determine whether the electric force between charged objects is attractive or repulsive based on the types of charges.
I can compare the electric interactions between charged objects in order to determine the charge of each object.

29. The Electric Force & Newton's 3rd Law
Being a force, the same laws and principles that describe any force describe the electrical force.
According to Newton's third law (the action-reaction law), a force is simply a mutual interaction between two objects that results in an equal and opposite push or pull upon those objects.

30. The Electric Force & Newton's 3rd Law
Object A exerts a rightward push upon Object B. Object B exerts a leftward push upon Object A.
These two pushing forces have equal magnitudes and are exerted in opposite directions of each other.
Why are these called repulsive forces?
Why do they objects repel in this situation?

31. The Electric Force & Newton's 3rd Law
Object C exerts a leftward pull upon object D. Object D exerts a rightward pull upon Object C.
Each object does its own pulling of the other.
These two forces have equal magnitudes and are exerted in opposite directions of each other.
However in this instance, the direction of the force on Object D is towards Object C and the direction of the force on Object C is towards object D. Because of the towards each other nature of the mutual interaction, the force is described as being attractive.

32. Interaction Between Charged and Neutral Objects
Any charged object - whether positively charged or negatively charged - will have an attractive interaction with a neutral object.
Positively charged objects and
neutral objects attract each other.
Negatively charged objects and

33. Electrical forces ____.
a. can cause objects to only attract each other b. can cause objects to only repel each other c. can cause objects to attract or repel each other d. have no effect on objects

34. The following charge interactions between balloons A, B & C are observed. It is known that balloon B is charged negatively. What can you conclusively confirm about the charge on balloon A & C.

35. Upon entering the room, you observe two balloons suspended from the ceiling. You notice that instead of hanging straight down vertically, the balloons seem to be repelling each other. You can conclusively say …
a. both balloons have a negative charge. b. both balloons have a positive charge. c. one balloon is charge positively and the other negatively. d. both balloons are charged with the same type of charge.

36. A student is investigating the charge on several objects and makes the following findings. He knows that object A is negatively charged and object B is electrically neutral. What can he definitively conclude about the charge on objects C, D, E, and F? Explain.

37. Two objects are charged as shown. Object X will ___ object Y.
a. attract b. repel c. not affect

38. Two objects are shown. One is neutral and the other is negative
Two objects are shown. One is neutral and the other is negative. Object X will ____ object Y.
a. attract b. repel c. not affect

39. Balloons X , Y and Z are suspended from strings as shown
Balloons X , Y and Z are suspended from strings as shown. Negatively charged balloon X attracts balloon Y and balloon Y attracts balloon Z. Balloon Z ____.
a. may be positively charged
b. may be negatively charged
c. may be neutral
d. must be positively charged
e. must be negatively charged
f. must be neutral

40. Learning Targets
I can describe the properties of insulators and conductors.
I can explain why an attractive force results from bringing a charged object near a neutral object.
I can draw the redistribution of electric charges on a neutral object when a charged object is brought near.

41. Conductors
The behavior of an object that has been charged is dependent upon whether the object is made of a conductive or a nonconductive material.
Conductors are materials that permit electrons to flow freely from particle to particle.
An object made of a conducting material will permit charge to be transferred across the entire surface of the object.
Conductors allow for charge transfer through the free movement of electrons.

42. Insulators
Insulators are materials that impede the free flow of electrons from atom to atom and molecule to molecule.
If charge is transferred to an insulator at a given location, the excess charge will remain at the initial location of charging.
The particles of the insulator do not permit the free flow of electrons.

43. Insulators
While insulators are not useful for transferring charge, they do serve a critical role in electrostatic experiments.
What are some important uses of insulators?

44. Examples of Conductors & Insulators
metals
Examples of insulators
aqueous solutions of salts
plastics
graphite
Styrofoam
the human body
paper
rubber
glass
dry air

45. One of these isolated charged spheres is copper and the other is rubber. The diagram below depicts the distribution of excess negative charge over the surface of two spheres. Label which is which and support your answer.

46. Which of the following materials are likely to exhibit more conductive properties than insulating properties?
a. rubber b. aluminum c. silver d. plastic e. wet skin

47. A conductor differs from an insulator in that a conductor ________.
a. has an excess of protons b. has an excess of electrons c. can become charged and an insulator cannot d. has faster moving molecules e. does not have any neutrons to get in the way of electron flow f. none of these

48. Suppose that a conducting sphere is charged positively by some method
Suppose that a conducting sphere is charged positively by some method. The charge is initially deposited on the left side of the sphere. Yet because the object is conductive, the charge spreads uniformly throughout the surface of the sphere. The uniform distribution of charge is explained by the fact that ____.
a. the charged atoms at the location of charge move throughout the surface of the sphere b. the excess protons move from the location of charge to the rest of the sphere c. excess electrons from the rest of the sphere are attracted towards the excess protons

49. When an oil tanker car has arrived at its destination, it prepares to empty its fuel into a reservoir or tank. Part of the preparation involves connecting the body of the tanker car with a metal wire to the ground. Suggest a reason for why is this done.

50. Polarization
In conducting objects, they are so loosely bound that they may be induced into moving from one portion of the object to another portion of the object.

51. Polarization of Conductors
Polarization is the process of separating opposite charges within an object.
The positive charge becomes separated from the negative charge.
By inducing the movement of electrons within an object, one side of the object is left with an excess of positive charge and the other side of the object is left with an excess of negative charge.
Charge becomes separated into opposites.
The polarization process always involves the use of a charged object to induce electron movement or electron rearrangement.

52. How Can an Insulator be Polarized?

53. Examples of Polarization

54. Polarization is Not Charging
When an object becomes polarized, there is simply a redistribution of the centers of positive and negative charges within the object.
There are still equal numbers of positive charges and negative charges within the object.
When neutral objects become polarized, they are still neutral objects.

55. A rubber balloon possesses a positive charge
A rubber balloon possesses a positive charge. If brought near and touched to the door of a wooden cabinet, it sticks to the door. This does not occur with an uncharged balloon. These two observations can lead one to conclude that the wall is _____.
a. electrically neutral b. negatively charged c. a conductor d. lacking electrons

56. Which of the diagrams below best represents the charge distribution on a metal sphere when a positively charged plastic tube is placed nearby?

57. The distribution of electric charge in a H2O molecule is nonuniform
The distribution of electric charge in a H2O molecule is nonuniform. The more electronegative oxygen atom attracts electrons from the hydrogen atom. Thus, the oxygen atoms acquire a partial negative charge and the hydrogen atoms acquire a partial positive charge. The water molecule is "polarized." Which diagram(s) below correctly portray(s) a pair of H2O molecules? Explain.

58. True or False: When an object becomes polarized, it acquires a charge and becomes a charged object.

59. Charged rubber rods are placed near a neutral conducting sphere, causing a redistribution of charge on the spheres. Which of the diagrams below depict the proper distribution of charge on the spheres? List all that apply.

60. In the above situation, the conducting sphere is ____
In the above situation, the conducting sphere is ____. List all that apply.
a. charged b. uncharged (neutral) c. polarized