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9/7-Homework
toc 1. What is the structure and properties of an atom? a. Anion is negative, Cation is positive b. Dense center with protons and neutrons, electrons orbiting in the electron clodu c. Electronegativity is how strongly an atom will hold onto its electrons

2. What is the symbol and unit of electric charge? a. Symbol is q or Q b. Unit is Coulombs c. +/- 1.6x10-19 C

3. Distinguish between positive and negative charges in as many ways as possible. a. Positive-- are ions, much larger, mass=10,000xelectrons, immobile b. Negative-- are electrons, much smaller, mass= 9.11x10-31 Kg, mobile

4. Describe the properties of electric forces. a. particles with like charges repel b. particles with different charges will attract

5. Distinguish between insulators and conductors. a. conductors are materials that permit electrons to flow freely b. insulators are materials that impede the free flow of electrons

6. What is the law of electric charge? a. all magnetic objects have the tendency to repel or attract on another b. the attraction/repulsion occurs in a straight line, there is a force between the charges and the bigger the charges the gretaer the force

7. What is polarization? a. the process of separating opposite charges within an object b. by inducing movement of electrons within an object, one side of the object is left with an excess positive charge and the other side of the object is left with an excess of negative charge

8. How does a neutral object acquire charge? a. induced polarization

9. Distinguish between the 3 charging processes. a. Frictional charging results in a transfer of electrons between the two objects that are rubbed together b. induction charging is a method used to charge an object without actually touching the object to any othre charged object c. Conduction charging is charging by contact, and requires a conductor

9/8-Homework Summary
1. What (specifically) did you read that you already understood well from our class discussion? Describe at least 2 items fully. a. I already had a pretty good understanding of the history of the atom from when I took chemistry. I also was well aware of the structure and properties of the atom. I knew about the subatomic particles and their charges. I already knew about electrically charged ions and neutral atoms. I was already aware that protons and electrons are attracted to each other because of their opposite charges. I also was aware of the definitions of conductors and insulators.

2. What (specifically) did you read that you were a little confused/unclear/shaky about from class, but the reading helped to clarify it? Describe the misconception you were having as well as your new understanding. a. Before reading the Physics Classroom I didn't know about Coulombs. I think the book did a good job of explaining this; I now know what they are and how many Coulombs are in one electron. I didn't know that Newton's Third Law of Action Reaction could be applied to magnetic forces, but the book did an adequate job of explaining this. I also didn't know that charged objects (negative or positive) are attracted to neutral objects. At first I was very confused about polarization, but now I understand it due to descriptions and examples in the text. It was a little confusing how polarization is not charging, but I was able to understand it based on the text.

3.What (specifically) did you read that you still do not understand? Please word these in the form of a question. a. I am a little confused about the polarization of insulators. Is the only way for an insulator to be polarized through a polar bond?

4. What (specifically) did you read that was not gone over during class today? a. In class prior to this reading we had not discussed polarization (or maybe that was what we were doing with our demonstrations?) or conductors and insulators.

9/9-Homework Summary

 * 1) What (specifically) did you read that you already understood well from our class discussion? Describe at least 2 items fully.
 * 2) I fully understood charging by induction from class. It is a kind of polarization that results in the object acquiring the opposite charge of the charging object. If a negative charging object is held towards the object, it will cause the electrons to repel. If the object is attached to a grounding wire, the electrons will flow through it, out of the object, resulting in the object being positively charged.
 * 3) I also fully understood charging by conduction from class. It is another kind of polarization that results in the object acquiring the same charge as the charging object. If a negative charging object is held towards the object, it will also cause the electrons to repel. The positive side of the object will attract the electrons in the charging object. The electrons enter the object, creating a negatively charged object, with more electrons than protons.
 * 4) What (specifically) did you read that you were a little confused/unclear/shaky about from class, but the reading helped to clarify? Describe the misconception you were having as well as your new understanding.
 * 5) I understood everything we discussed in class adequately.
 * 6) What (specifically) did you read that you still don’t understand? Please word these in the form of a question.
 * 7) The physics classroom explained everything clearly and I have no questions.
 * 8) What (specifically) did you read that was not gone over during class today?
 * 9) The Law of Conservation of Charge was not gone over in class, but I understand it.

9/12-Sticky Tape Lab










9/13-Homework Summary

 * 1) What (specifically) did you read that you already understood well from our class discussion? Describe at least 2 items fully.
 * 2) I was not in class today so I didn't already understand anything that I read. I also didn't know what we did or did not go over.
 * 3) What (specifically) did you read that you were a little confused/unclear/shaky about from class, but the reading helped to clarify? Describe the misconception you were having as well as your new understanding.
 * 4) Although I wasn't in class today, I understood a lot from the reading. I understood the discussion about Newton's Laws applying to electrical forces, and about electrical forces being in equilibrium. The diagrams of the two-liked charged balloons were very helpful. I also understood the discussion of force as a vector quantity, and the different variables that can affect the magnitude of this vector. I also really understood the reasoning and calculations of Coulomb's Law. The example calculations were very helpful. I also fully understood the Inverse Square Law. I understood the calculations describing how to find acceleration based off of the electrical force and the gravitational force using vector addition.
 * 5) What (specifically) did you read that you still don’t understand? Please word these in the form of a question.
 * 6) How did the physics classroom get the direction of the forces in the 3 charge equation based on their calculations?
 * 7) Can we do a similar problem to this in class?
 * 8) What (specifically) did you read that was not gone over during class today?
 * 9) I was not in class today so I do not know what was or was not gone over.

9/14-Homework Questions
1. What is an electric field? a. an electric field is when and electric force acts over the distances separating two charged objects

2. What are the characteristics and properties of an electric field? See applet: []  a. the magnitude of the electric field depends on the charged object, and the distance from the field. 3. What are the “players” involved in an electric field? a. distance, charge of object 1, and charge of object 2

4. What are electric field lines? a. vectors that point in the direction that a positive test charge would accelerate if placed upon the line

5. What are 4 characteristics of electric field lines? a. always extend from a positively charged object to a negatively charged object, from a positively charged object to infinity, or from infinity to a negatively charged object b. never cross each other c. most dense around the objects with the most amount of charge d. at locations where electric field lines meet the surface of an object, the lines are perpendicular to the surface

6. Go to []. Scroll to the bottom of the page and do the “Check Your Understanding” questions. 1. C, the lines are directed the wrong way D, the lines are not evenly distributed E, the lines are directed the wrong way 2. The lines cannot intersect  3. D  4. D, A, E, C, B  5. positive- A, C, F, G, H, I negative-B, D, E  6. B then A, C then D, G then E then F, J then H, then I  9/15-Homework Summary **Action At a DIstance: An Electric Field is created by a charged object and is dependent on the charge the creates the field and the distance from a charge.**

The concept of a **field force** is utilized by scientists to explain this rather unusual force phenomenon that occurs in the absence of physical contact. While all masses attract when held some distance apart, charges can either repel or attract when held some distance apart

A charged object creates an electric field - an alteration of the space in the region that surrounds it. Other charges in that field would feel the unusual alteration of the space.

In the same manner, an electric charge creates an electric field - it has altered the nature of the space surrounding the charge. And if another charge gets near enough, that charge will sense that there is an affect when present in that surrounding space. the strength of the electric field is dependent upon the amount of charge that creates the field and the distance from the charge.



**Electric Field Intensity: An Electric Field made by a source charge, is felt by a test charge and the strength of an electric field is inversely related to the distance from the source charge.** Electric field strength is [|a vector quantity] ; it has both magnitude and direction

This electric charge creates an electric field; since **Q** is the source of the electric field, we will refer to it as the **source charge**.

The charge that is used to measure the electric field strength is referred to as a **test charge** since it is used to //test// the field strength.

When placed within the electric field, the test charge will experience an electric force - either attractive or repulsive. Electric field is the force per quantity of charge //on the test charge//.

The strength of an electric field as created by source charge **Q** is inversely related to square of the distance from the source. This is known as an **inverse square law**.

Electric field strength is location dependent, and its magnitude decreases as the distance from a location to the source increases.

The magnitude of the electric field vector is calculated as the force per charge on any given test charge located within the electric field.

The force on the test charge could be directed either towards the source charge or directly away from it.



**Electric Field Lines: Electric field lines are directed from positively charged objects to negatively charged objects, can never intersect, are most dense around objects with the greatest charge, and are perpendicular to surfaces.**

**electric field lines** are directed away from positively charged source charges and toward negatively charged source charges One common convention is to surround more charged objects by more lines.

• Electric field lines always extend from a positively charged object to a negatively charged object, from a positively charged object to infinity, or from infinity to a negatively charged object. • Electric field lines never cross each other. • Electric field lines are most dense around objects with the greatest amount of charge. • At locations where electric field lines meet the surface of an object, the lines are perpendicular to the surface.



**Electric Fields and Conductors: When dealing with conductors at equilibrium, the electric field anywhere beneath the surface of the charged conductor is zero. Conductors at equilibrium also have electric fields that are perpendicular to surfaces, and the electric fields are strongest where the object is most curved.**

[|a conductor] is material that allows electrons to move relatively freely from atom to atom.

**Electrostatic equilibrium** is the condition established by charged conductors in which the excess charge has optimally distanced itself so as to reduce the total amount of repulsive forces. Once a charged conductor has reached the state of electrostatic equilibrium, there is no further motion of charge about the surface.

One characteristic of a conductor at electrostatic equilibrium is that the electric field anywhere beneath the surface of a charged conductor is zero. This of course presumes that our conductor does not surround a region of space where there was another charge.

A second characteristic of conductors at electrostatic equilibrium is that the electric field upon the surface of the conductor is directed entirely perpendicular to the surface. There cannot be a component of electric field (or electric force) that is parallel to the surface A third characteristic of conducting objects at electrostatic equilibrium is that the electric fields are strongest at locations along the surface where the object is most curved. A flat location has no curvature and is characterized by relatively weak electric fields. On the other hand, a //blunt point// has a high degree of curvature and is characterized by relatively strong electric fields.

**Lightning: Lighting is caused by the polarization of clouds, in which positive charges move to the top and negative charges move to the bottom.** The precursor of any lightning strike is the [|polarization] of positive and negative charges within a storm cloud.

Two mechanisms seem important to the polarization process. One mechanism involves a separation of charge by a process that bears resemblance to [|frictional charging].

Upwardly rising moisture collides with water droplets within the clouds. In the collisions, electrons are ripped off the rising droplets, causing a separation of negative electrons from a positively charged water droplet or a cluster of droplets.

These cooler temperatures cause the cluster of water droplets to undergo freezing. The frozen particles tend to cluster more tightly together and form the central regions of the cluster of droplets. The frozen portion of the cluster of rising moisture becomes negatively charged and the outer droplets acquire a positive charge.

Electrons on Earth's outer surface are repelled by the negatively charged cloud's bottom surface. This creates an opposite charge on the Earth's surface. Buildings, trees and even people can experience a buildup of static charge as electrons are repelled by the cloud's bottom.

Classwork