4 Haziran 2013 Salı

Preparation and application of worksheets

·         To know the basic concepts related to the subject area.
·         To prepare a material appropriate for the students’ age, knowledge & etc.
·         To use the learning-teaching tools effectively.
·         To evaluate the students’ works.
·         To give feedback on time.

Behaviours that worksheet includes:
·         General objectives:
-Students will know the terms about the topic of electrostatic. (Knowledge level)
-Students will comprehend the basic concepts about the topic of electrostatic. (Comprehension level)
-Students will apply what they learned in new or different situations related to electrostatic. (Application level)

·         Specific objectives :
-Students discover that matters can be charged by gaining and loosing electrons. (Synthesis level)
General evaluation of this worksheet’s application: In this worksheet, I analyzed the problem solving process of students, so students worked in this worksheet by individually. If I was a teacher in this class, I use this worksheet at the end of the class hour after I talked about this topic. I gave them 30 minutes to solve these questions. My first student’s name is Başak. According to my cooperative teacher, she is not so successful student but I want to see whether my worksheet is suitable. When she was solving the worksheet, she answered correctly multiple choice questions but she couldn’t solve the open ended questions. I think she doesn’t try to force her brain when she is solving question. According to this worksheet, I concluded that she has no problem with solving skills. Generally, this worksheet is not useful for the unsuccessful and dilatory students but the pictures are effective for the student’ attention. After I took feedback from my plot student, I presented this worksheet to another student. My second student is also in the same class. Her name is Gözde. This student is one of the successful students in the same class. When I asked her to do the worksheet, she accepted me politely. Worksheet drew her attention. Again I observed her when she was solving questions. Firstly, she read the topic part and then tried to solve the questions. While she was solving multiple choice questions, she had not any problems. She tried to solve the questions. She solved the question at 25 minutes. After this feedback, I think that I can prepare all types of questions. The question part of the worksheet is really good but topic part is a little bit long. Students had no difficulties while understanding and solving worksheet entirely. 

Name & Surname:

(Figure 1)
All material objects are composed of atoms. There are different kinds of atoms known as elements. These elements can combine to form compounds.
Material objects are composed of atoms and molecules of these elements and compounds. The nucleus of the atom contains positively charged protons and neutral neutrons.
These protons and neutrons are not removable or perturb able by usual everyday methods.
One sure truth of this unit is that the protons and neutrons will remain within the nucleus of the atom.
Electrostatic phenomenon can never be explained by the movement of protons.
1-      Charging

·         By transferring electrons from one place to another, we can do this by physical contact,
    (substances are rubbed together or simply touched.)

·         Or we can redistribute the charge on an object simply by putting a charged object near it -this is called induction.

2-      Methods of Charging

a)      Charging by friction
We are all familiar with the electrical effects produced by friction.
We can stroke a cat's fur and hear the crackle of sparks that are produced, or comb our hair in front of a mirror in a dark room and see as well as hear the sparks.
We can scuff our shoes across a rug and feel a tingle as we reach for the doorknob.

b)     Charging by induction
If you bring a charged object near a conducting surface, you will cause electrons to move in the surface material even though there is no physical contact.
Consider the two insulated metal spheres, A and B, in the Figure.
(A) They touch each other, so in effect they form a single non-charged conductor.
(B) When a negatively charged rod is brought near A, electrons in the metal, being free to move, are repelled as far as possible until their mutual repulsion is big enough to balance the influence of the rod. Charge is redistributed.
(C) If A and B are separated while the rod is still present,
(D) they will each be equal and oppositely charged. This is charging by induction. 
             A                         B                          C                         D

(Figure 2)
c)      Charging by contact
Charging by contact is transfer of electric charges between objects by rubbing or simple touching.
For example, when a negatively charged rod is placed in contact with a neutral object, some electrons will move to the neutral object.
This method of charging is simply called charging by contact.
If the object is a good conductor, electrons will spread to all parts of its surface because the transferred electrons repel one another.
If it is a poor conductor, it may be necessary to touch the rod at several places on the object in order to get a more or less uniform distribution of charge.

(Figure 3)


*Use your understanding of concept to answer the following questions. Try to fill in the blanks with most appropriate words or phrases that you could find.

1)      __________ & __________ are the charged parts of an atom.
2)      A plastic strip was rubbed with cotton and became positively charged. The correct explanation for why the plastic strip becomes positively charged is that__________________________________________________________________.

3)      A positively charged balloon is brought near a neutral conducting sphere as shown below. While the balloon is near, the sphere is touched (grounded).
                                          (Figure 4)
      At this point, there is a movement of electrons. Electrons move _________________.

*Decide due to given situation, whether the following statements are true or false.


a) A physics teacher rubs a glass object and a felt cloth together and the glass becomes positively charged.
The glass gained protons during the rubbing process. (_____)
The felt became charged negatively during this rubbing process. (_____)
Charge is created during the rubbing process; it is grabbed by the more charge-hungry object. (_____)
If the glass acquired a charge of +5 units, then the felt acquires a charge of -5 units. (_____)
This event violates the law of conservation of charge. (_____)
Electrons are transferred from glass to felt; protons are transferred from felt to glass. (_____)
Once charged in this manner, the glass object and the felt cloth should attract each other. (_____)
In general, glass materials must have a greater affinity for electrons than felt materials. (_____)
b) Two neutral conducting pop cans are touching each other. A negatively charged balloon is brought near Can X as shown below. As the balloon approaches Can X, there is a movement of electrons between the balloon and can X (in one direction or the other). (_____)

*Give an answer and shortly explain your reasoning in the following question.

5)    Saran Wrap has a larger electron affinity than Nylon. If Nylon is rubbed against Saran Wrap, which would end up with the excess negative charge? _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________.

*Choose and circle the correct answer due to you. 

6)   Which statement best explains why a rubber rod becomes negatively charged when rubbed with fur?
a. The rubber that the rod is made of is a better insulator than fur.
b. The fur is a better insulator than the rubber.
c. Molecules in the rubber rod have a stronger attraction for electrons than the molecules in the fur.
d. Molecules in the fur have a stronger attraction for electrons than the molecules in the rubber rod.
7)      A neutral metal sphere is touched by a positively charged metal rod. During the process, protons are transferred from the _____ to the _____ and the sphere acquires a _____ charge.
a. charged rod, neutral sphere, negative
b. charged rod, neutral sphere, positive
c. neutral sphere, charged rod, negative
d. neutral sphere, charged rod, positive
e. ... nonsense! None of these describe what occurs.
8)      A positively charged pop can is touched by a person standing on the ground. The pop can subsequently becomes neutral. The pop can becomes neutral during this process because ______.
a. electrons pass from the pop can to the person (ground)
b. electrons pass from the person (ground) to the pop can
c. protons pass from the pop can to the person (ground)
d. protons pass from the person (ground) to the pop can

1)      Electrons & Protons
Electrons are negatively charged and protons are positively charged. The neutrons do not have a charge.
2)      ‘...the plastic strip lost electrons to the cotton during the charging process.’
When two different materials are rubbed together, there is a transfer of electrons from one material to the other material. This causes one object to become positively charged (the electron loser) and the other object to become negatively charged (the electron gainer).
3)      ‘...into the sphere from the ground (hand).’
Since the balloon is not contacted to the sphere, electrons do NOT move between the balloon and the sphere (ruling out choices c, d, e, and f). The presence of the positive balloon draws electrons from ground to the sphere. This is the principle of opposites attract.
4)      a) F – T – F – T – F – F – T – F
For false ones, the explanations are in order like below.
*protons are not transferred in electrostatics.
*charge is neither created nor destroyed (ever).
*electrons are simply transferred, consistent with the law of conservation of charge.
*protons are not transferred in electrostatic experiments (the electrons are transferred).
*If glass transfers electrons to felt, then the felt must be more electron-hungry.

b) F
In induction charging, there is never a transfer of electrons between the charged object (the balloon) and the object being charged (Can X). The electron movement happens between the object being charged (Can X) and the ground (Can Y). In this case, electrons would leave Can X and enter Can Y.
5)      ‘saran wrap’
(When two materials are rubbed together, the material with the greatest affinity for electrons is the material which takes electrons away from the other material. Saran wrap takes electrons from nylon and acquires the negative charge. In turn, the nylon loses electrons and becomes charged positively.)
6)      ‘C’
During a charging by rubbing (or by friction) process, the material that becomes negatively charged does so because it simply likes electrons more than the material with which it is rubbed. The conductive abilities of the two materials has nothing to do with the subsequent result of the rubbing process.
7)      ‘E’
Protons are never transferred in electrostatic activities. In this case, electrons are transferred from the neutral object to the positively charged rod and the sphere becomes charged positively.
8)      ‘B’
Protons do NOT move during electrostatic activities, so choices c and d can be ruled out. To ground a positively charged object, electrons must be added to it in order neutralize its excess positive charge. So electrons must move from the ground into the pop can.