Ch18_LitmanovP

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= Guiding Questions 1-9 =


 * 1) What is the structure and properties of an atom?

-An atom consists of a nucleus and electrons.

-The nucleus is made of Protons and Neutrons bound together. The protons are positively charged and the neutrons have a neutral charge.

-The electrons orbit the nucleus and are much smaller than the protons and neutrons. They have a negative charge and can be released from the atom if it receives enough energy.

2. What is the symbol and unit of electric charge?

-A Coulomb is the unit of electric charge.

-The symbol of a Coulomb is a C

-Symbol of charge is Q

3. Distinguish between positive and negative charges in as many ways as possible.

-Positive charges are from when there are fewer electrons than protons.

-Negative charges are from when there are more electrons than protons.

4. Describe the properties of electric forces.

-Electric forces can have a non-impact influence on other objects.

-Opposite electric forces attract. (Attractive)

-Same charged electric forces repel. (Repulsive)

-Charged and neutral objects can attract.

5. Distinguish between insulators and conductors.

-Conductors are materials that allow electrons to flow freely from atom to atom and molecule to molecule. Conductors permit charge to be transferred across the surface of the object.

-Insulators do not allow electrons to flow freely from atom to atom and molecule to molecule. Charge introduced will remain at the site where the charge was introduced. Charge is rarely distributed evenly across the surface of the object.

6. What is polarization? -The build up of positive and negative charges on separate sides of an object. The site of positive charge and negative charge are opposite one another and are called ‘poles’.

7. How does a neutral object acquire charge? -When a charged object comes near a neutral object, the neutral object polarizes, and creates a positively charged pole and negatively charged pole on opposite sides of the neutral object. The charged object attracts to the pole with an opposite charge from that object.

8. Distinguish between the 3 charging processes. -Polarization creates charge in a neutral object WITHOUT removing or adding any electrons. The positive and negative charges separate and create two poles on opposite sides of the object. The charge is not as strong as if an electron were added or removed, but the object will still have an electric force. -By giving enough energy to an electron, it will leave an atom and create a positively charged ion. This process removes an electron and creates a strong positive electric force. -Some atoms will add more electrons and become a negatively charged ion. This process adds an electron and creates a strong negative electric force.

9. What is the law of electric charge?

-Opposites attract and likes repel.

= Summary: Lesson 1 =

1. What (specifically) did you read that you already understood well from our class discussion? Describe at least 2 items fully.

I already understood the structure of the atom when I read about it on the physics classroom. I understand well that an atom has a nucleus which is comprised of positive, neutral, and negative particles. Positive being the protons, neutral being the neutrons, negative being the electrons. An atom can also be charged. Positively charged if it has less electrons than protons and negatively charged if it has more electrons than protons.

I also understood the idea of attraction and repulsion. If a negatively charged object is placed near another negatively charged object the objects will repel each other. The opposite is also true, if a positively charged object is placed near a negatively charged object, they will be attracted to each other. Opposites attract and likes repel. Additionally, any charged object will be attracted to a neutral object.

2. 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.

In class I was a little confused about what polarization was and how an object becomes polarized. I understand now that polarization means charges within an object move to one side or the other so that one portion of the object appears to be charged. However, the net charge of the object is still neutral and polarization is not the same as charging. An object becomes polarized when a charged object comes close, but does not touch, a neutral object. The proximity of the charged object causes the charges in the neutral object to move towards the charged object or away from it.

3. What (specifically) did you read that you still don’t understand? Please word these in the form of a question.

I understood everything.

4. What (specifically) did you read that was not gone over during class today? N/A

= Summary: Lesson 2 =

1. What (specifically) did you read that you already understood well from our class discussion? Describe at least 2 items fully.

I understood charging an object by induction. Two touching neutral objects become polarized when a charged negative (or positive) object comes close. The negative charges moves from the near object to the far object and the objects become polarized. When the objects are separated, they are charged. The near object has a deficiency of negative charge, making it positive, and the far object has an excess of negative charge, making it negative.

I also understood charging by friction. Different objects have different a different amount of "love" for electrons. When two objects are rubbed together, the object that "loves" electrons more receives the electrons from the other object leaving both objects charged.

2. 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.

I understood everything from our class discussion

3. What (specifically) did you read that you still don’t understand? Please word these in the form of a question.

Everything was explained well. I have no questions

4. What (specifically) did you read that was not gone over during class today?

We did not go over the Law of Conservation of charge, but it makes sense to me.

=Sticky Tape Lab/Activity=


 * Materials**

- tape, foil, paper, scissors, PVC rod

close enough to affect each other.
 * Observations**
 * #5: Sketch with labeled force vectors for two top tapes

Repel

<- Top Top -> || Sketch with labeled force vectors for two top tapes half as far apart as left sketch

Repel

<- Top Top -> ||
 * #8: Describe paper on paper interaction

N/A || #9: Describe foil on foil interaction

N/A ||
 * #13: Describe top tape and foil interaction

Attract Diagram with forces

Top -> <- Foil || Describe top tape and paper interaction

Attract

Diagram with forces

Top -> <- Paper ||
 * #13: Describe top tape and top tape interaction

Repel

Diagram with forces

<- Top Top -> || Describe top tape and bottom tape interaction

Repel

Diagram with forces

<- Top Paper -> ||
 * #13: Describe bottom tape and foil interaction

Attract

Diagram with forces

Bottom -> <- Foil || Describe bottom tape and paper interaction

Attract

Diagram with forces

Bottom -> <- Paper ||


 * #13: Describe bottom tape and top tape interaction

Attract

Diagram with forces

Bottom -> <- Top || Describe bottom tape and bottom tape interaction

Repel

Diagram with forces

<- Bottom Bottom -> ||
 * #14: Describe PVC rod and paper interaction

strong attraction || Describe PVC rod and foil interaction

Strong attraction ||
 * #14: Describe PVC rod and top tape interaction

strong attraction || Describe PVC rod and bottom tape interaction

Strong attraction ||
 * #15: Describe Lucite rod and paper interaction

strong attraction || Describe Lucite rod and foil interaction

strongest attraction ||
 * #15: Describe Lucite rod and top tape interaction

Strong Attraction || Describe Lucite rod and bottom tape interaction

Strong attraction ||
 * #16: State top and top tape interaction based on charge

They should repel || State top and bottom tape interaction based on charge

They should attract ||
 * #16: State bottom and bottom tape interaction based on charge

they should repel ||  ||


 * Discussion Questions **


 * 1) Explain how materials become charged through their interaction with one another.

In this activity/lab the tape was charged by friction. When we pulled the tapes apart or rubbed the rod with fur, we polarized the objects through friction.


 * 1) Why, when you stroke a cat's fur, or comb your hair on a cold, dry day can you hear a crackling sound? Doing these things in a darkened room, you can actually see sparks. Explain.

The crackling noise is the transfer of electrons from one object to another.


 * 1) Photocopying machines use the principles of electric charges. Do research to find out how photocopying machines work. Be sure to list your sources.

An image is projected onto a drum (which has a positive charge). This drum conducts electricity when under light. The toner has a negative charge and is attracted to the positively charged parts of the drum (where the outline of the image is). The drum rotates and imprints the image onto a piece of paper. By heating the paper the image is “fixed” onto the paper permanently.

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 * 1) Materials have a characteristic which evaluates their attraction for electrons. The Triboelectric Series orders materials by their affinity for gathering electrons through contact from other materials. The materials toward the top of the list are likely to give up electrons in these interactions whereas those at the bottom are more likely to gain electrons. Five materials are ranked as follows, with more positives meaning least desiring electrons.

PVC(++), Wool (+++++), Styrene (++++), Teflon (+), Polyester (+++)

b. Determine the net charge on each item when the following pairs of materials are rubbed together. (In other words, which ends up giving up electrons and which ends up accepting them?)

i. PVC and Wool

PVC (-) Wool (+)

ii. PVC and Teflon

Teflon (-) PVC (+)

iii. PVC and Polyester

PVC (-) Polyester (+)

iv. Teflon and Polyester

Teflon (-) Polyester (+)

v. Styrene and Wool Styrene (-) Wool (+)

= Summary: Lesson 3 = 1. What (specifically) did you read that you already understood well from our class discussion? Describe at least 2 items fully.

I understand that charge interactions are forces and that electric force is a vector quantity with magnitude and direction. Direction is determined by attraction or repulsion between two objects and magnitude is determined by charge and distance.

I also understand the inverse square law and that force and distance have an inverse square relationship. When distance between two charges increases, the force decreases and vice versa.

2. 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.

At first I didn't understand how charges could act as forces on each other but the reading made it clear that electrostatic force is similar to gravitational force.

3. What (specifically) did you read that you still don’t understand? Please word these in the form of a question.

I understood everything.

4. What (specifically) did you read that was not gone over during class today?

We did not go over how to solve problems which deal with charges in equilibrium.

Coulomb's Law of Electric Force
 * The three variables that affect electric force are charge, charge, and distance. The force is determined by the charge of the two different objects involved, as well as their distance away.
 * The equation of Coulomb's Law is F = (k x Q 1 x Q 2 ) / d 2 Q = charge of either object k= 9 x 10 9 Nm 2 /C 2

Inverse Square Law
 * Inverse square relationships are when the decrease of a number increases another number by a square value. For example, electrostatic forces between two points varies inversely with the square of the distance apart.

Newton's Laws and the Electrical Force = = = = =**Guiding Questions 10-15**=
 * the force attracting or repelling two charged objects id electrical force.
 * This force follows Newton's Laws of motion. It causes acceleration in objects, such as a balloon.
 * Electrical force is also seen when objects repel, and are at an angle while in static equilibrium. The electrical force causes the objects to stay separated.
 * With three or more charged objects, the equations do not have to be changed!
 * Each force can be treated as a vector, and added to discover where something would move as a result. In four objects, there would be three forces impacting each charged object.

10. What is an Electric Field?

The electric field is the area around a charge where another charge will feel the electric force.

11. What are the characteristics and properties of an electric field? - Electric Fields are perpendicular to surface of an object. - Beneath the surface electric field is 0 - Electric Field is strongest at points which are most pointed.

12. What are the “players” involved in an electric field? There is a source charge and experiencing charge. The source charge is represented by Q and experiencing charge is represented by q. Source gives off the electric field and experiences "feels" the effects of that electric field.

13. What are electric field lines? They are lines used to visually represent electric fields

14. What are 4 characteristics of electric field lines? - Electric field lines go out of positive to infinity and from infinity and into negative - Lines never intersect - Field lines are more dense around objects with greater charge - Lines always meet the surface of an object perpendicularly

15. Go to []. Scroll to the bottom of the page and do the “Check Your Understanding” questions.

1. Correct: A,B. Incorrect: C,D,E. C is incorrect because the lines are going into positive. D is incorrect because the lines are more dense on one side of the object - the object is a symmetrical sphere so the lines should be even. E is incorrect because the lines are going out of negative.

2. The lines should never intersect.

3. D

4. D,A,E,C,B

5. A,C,F,G,H,I are positively charged. B, D, F are negatively charged

6. B < A; C < D; G < E < F; J < H < I

= Summary: Lesson 4 =

Action-at-a-distance forces are sometimes referred to as field forces. 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. An alternative to describing this action-at-a-distance affect is to simply suggest that there is something rather strange about the space surrounding a charged object. Any other charged object that is in that space feels the affect of the charge. 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. Whether a charged object enters that space or not, the electric field exists.
 * The Electric Field Concept **

Electric field strength is [|a vector quantity] ; it has both magnitude and direction. The magnitude of the electric field strength is defined in terms of how it is measured. Let's suppose that an electric charge can be denoted by the symbol ** Q **. 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 strength of the source charge's electric field could be measured by any other charge placed somewhere in its surroundings. 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. The test charge has a quantity of charge denoted by the symbol ** q **. When placed within the electric field, the test charge will experience an electric force - either attractive or repulsive. As is usually the case, this force will be denoted by the symbol ** F **. The magnitude of the electric field is simply defined as the force per charge on the test charge. The standard metric units on electric field strength arise from its definition. Since electric field is defined as a force per charge, its units would be force units divided by charge units. In this case, the standard metric units are Newton/Coulomb or N/C. = = 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. The worldwide convention that is used by scientists is to define the direction of the electric field vector as the direction that a **positive test charge** is pushed or pulled when in the presence of the electric field.
 * The Force per Charge Ratio **
 * The Direction of the Electric Field Vector **

Electric Field Lines
 * Electric field lines **, point in the direction that a positive test charge would accelerate if placed upon the line. As such, the lines are directed away from positively charged source charges and toward negatively charged source charges.


 * Rules for Drawing Electric Field Patterns **
 * 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.

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. If the conducting object is spherical, then this means that the perpendicular electric field vectors are aligned with the center of the sphere. If the object is irregularly shaped, then the electric field vector at any location is perpendicular to a tangent line drawn to the surface at that location. 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. The curvature of a surface can range from absolute flatness on one extreme to being curved to a //blunt// point on the other extreme. 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. A sphere is uniformly shaped with the same curvature at every location along its surface. As such, the electric field strength on the surface of a sphere is everywhere the same.
 * Electric Fields and Conductors **
 * 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.
 * Electric Fields are Perpendicular to Charged Surfaces **
 * Electric Fields and Surface Curvature **

=**Balloon Activity**=

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= = =Electric Field notes=



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