cognitive conflict - an example

Grade Level: 10^th Grade      Unit: Electricity

Chapter: Electric Charges   Topic: Properties of Electric Charges

Objective: Students discover that matters can be charged by gaining and loosing electrons.

Misconceptions:

·         The only charge of charged object is that it was charged.

·         A neutral object has any charge.

Main Questions:

·         Which characteristics does an object have for that it is charged?

·         Which characteristics does an object have for that it is neutral?

Other Questions:

·         Are there only negative charges in a negative charged particle?

·         Are there only positive charges in a positive charged particle?

·         Are there any charges in neutral objects?

Remembering of previous knowledge: Positive charges can not move because positive charges mean protons in the atom, but negative ones can move.

Anomalous Data:

1.      COLLECTING DATA AND DISCUSSING WITH FRIENDS

·         Here, students make a small experiment to see the truth on their own by following the steps given.

Students’ thought style: ‘Positively charged electroscope’s leaves become closer when we approached the  negatively charged rub near to electroscope’s knob because positive charges move from leaves to knob because of the attraction force. Then, electroscope’s leaves come more closer because of the same reason. Leaves became far again because maybe the charges in the rob neutralize in some amount because of our body and positive charges go to leaves again.’

·         After this explanation of students, we ask ‘why?’ questions below and again remembered the previous knowledge pointed above. At the final, teacher gives the scientific explanation.

ü  Rub a straw and then load the electroscope by induction. Next, when you draw near the same straw, the leaves begin by falling down. WHY?

ü   Bring the straw nearer to the plate. The leaves then diverge. WHY?

2.      TEACHER’S EXPLANATION AFTER ALL DISCUSSIONS

Charged by induction with a negative straw the electroscope has become positive (fig. 9). See the experiment called charging by induction. The negative straw will attract positive charges on the plate and repel more negative charges toward the leaves more it is near. Therefore,

The leaves falling down (fig. 12) because they are less positive ;

The leaves in close contact (fig. 13) when they are neutral ;

Then the leaves repelling again (fig. 14) when they become negative.

RESULT: So charged objects have not only charges that is the same as that they have. Only thing is that the number of same kind of charge that they have  is over. Neutral objects have both negative and positive charges in same number. Otherwise, if that was true, when the negative charged particle bring closer to positive charged electroscope, firstly, leaves of the electroscope gets closer to each other than,slowly they closed, consequently it can not be charged negatively because there was no any contact between electrification object and electroscope.

Giving Concept:

1.      Teaching strategy:

We found “inquiry based learning” method appropriate for this lecture. Inquiry-based learning is a student-centered and teacher-guided instructional approach that engages students in investigating real world questions that they choose within a broad thematic framework. Inquiry-Based learning complements traditional instruction by providing a vehicle for extending and applying the learning of students in a way that connects with their interests within a broader thematic framework. Students acquire and analyze information, develop and support propositions, provide solutions, and design technology and arts products that demonstrate their thinking and make their learning visible.

2.      Steps which will be followed during lecture:

a)       ‘Cognitive conflict.’

In order to overcome students’ misconceptions and make conceptual change; we will make students to do a mini experiment to see anomalous data. Then we will discuss the reasons of the situation in the experiment.

b)      Make groups and distribute the other activity sheets related to topic and the objective chosen. Doing activities and controlling the students while they do demos.

After discussing video, we will distribute the activity sheets to students and give them enough  time for doing the activities and answer the questions in this sheets. There are three different activities and groups could be formed by 3 to 5 students. While students do the demos, we will control and help them about their faults.

c)      Let students to explain what they have done.

After collecting evaluation sheets, we will let students to explain what they have done in each activity. Every group will choose a talker for their group and these students will explain groups’ ideas.

d)      Explain briefly the students’ results.

After students finis their explanations, we will briefly explain their results and if there will a wrong thing in their explanations we will correct them.

e)      Give the concept effectively. Talk about similar examples.

We will again talk about the concept and give effective explanations again. After giving concept, we will talk about two similar examples with the help of the slides.

     Activity – 1- Attraction of the Balloon

Materials: A balloon, a paper handkerchief, a wall.

Procedure: Inflate a balloon. Rub the top of the balloon with a paper handkerchief. Push it delicately to the ceiling.

Questions: What did you observe? What is the reason?

     Activity – 2- Bending water with a straw

Materials: A straw, a plastic cup that has a small hole at the bottom of it, water.

Procedure: One of the testers holds the cup. Other tester fills the cup with water. Charge the straw with hair. Bring the straw close to the stream of water.

Questions: What did you observe? What is the reason?

     Activity -3- Dancing fleas

Materials: Plexiglas sheet, a piece of wool, paper squares.

Procedure: Put paper squares on the table. Put Plexiglas on paper squares. Rub the top of the Plexiglas.

Questions: What did you observe? What is the reason?

References:

—Kalyoncu, C., Tütüncü, A., Değirmenci, A., Çakmak, Y., & Bektaş, E. (2008). Ortaöğretim Fizik 9 Ders Kitabı. Istanbul: MEB.

—Tsokos, K. A. (2008). Physics for IB Diploma (Fifth ed.). Cambridge: Cambridge University Press.

—Mausian, M., (n.d) , Attracted balloon , Retrieved December 20 , 2012,from University of Nantes, Electrostatic Experiment web site:  http://www.sciences.univ-nantes.fr/sites/michel_maussion/statelec/PagesEngl/02Balloon.html

—Ben Franklin's Secret Message (2006), Retrieved from http://www.physicscentral.com/experiment/physicsquest/past/upload/pq06-Extension1.pdf