Electrostatic Force and Its Effect on Our Life: a Basic Scientific Temperament - Outline Example

LESSON OBJECTIVES: 1. Making the students understand the manner in which science affects all of us in the activities of daily routine. 2. Understanding how some the electrostatic force helps in keeping a natural balance 3. Trying to decipher some scientific principles with the help of simple experiments. 4. Encouraging the scientific spirit amongst the students by making the study of science as simple and student friendly. KEY CONCEPTS/IDEAS: 1. Elementary Behaviour of Charge 2. The Law of charges 3. Electrostatic Force 4. Gravitational force 5. Van der Graaff Generator 6. Coulomb’s Law 7. Concept of static charge SYLLABUS LINK: Prescribed Focus Area (PFA) Electrostatic Force and its effect on our life Knowledge and Understanding It requires; A basic scientific temperament Eye for observations Desire to learn Readiness to devote some time Skills i. Awareness about some of the scientific terms ii. Ability to carry out some experiments Values and Attitudes i. Inquisitiveness ii. Patience during the experiments iii. Disciplinary attitude and temperament to follow the instructions PLAN: TIME TEACHER ACTION STUDENT-CENTRED ACTIVITIES (including assessment of learning) RESOURCES OPENING (About 10-15 minutes) Teacher gives some hints to the students like; i. Trying to come out with their responses Dry pieces of paper Comb Pen After calling the rolls, the teacher would call upon the students to come out with some peculiar situation, when they might have experienced some unexplained force while doing routine actions like opening the cupboard door, i. Experience of an electrical shock when we touch the cupboard handle after returning home from outside ii. While combing dry hair, sometimes the hair gets attracted towards the comb, instead of settling down. iii. Encouraging the students to come out with such experiences iv. Giving some hints about the static charge ii. Discussing their experiences amongst themselves and further refining their responses. iii. Quality Time Black-Board Marker Balloons Perspex rods Thread Ebonite rod Some wool or woollen jacket Silk cloth MAIN BODY i. Concept of Electric charges at rest i.e. electrostatics ii. Conduction of experiments Experiment-1 Students are asked to repeat the comb experiment Experiment-2 Students are then asked to do the balloon experiment. (35-40 Minutes) iii. Experiment-1: Teacher takes out a comb. Uses it on his dry hairs. Then shows how the comb is able to attract small pieces of paper kept on the table. In the comb experiment, students are asked to spread some small pieces of paper over a table. Then they are asked to take a comb and do the combing on their hairs. The ‘charged up’ comb is then taken near the pieces of paper. The comb starts attracting the paper pieces. In the balloon experiment, two balloons are charged up. One of the balloons is hanged up with a string. Care must be taken to see that the room where this experiment is being conducted must be free from airflows. Fans, blowers etc must also be switched off during the experiment, so that the balloon hung up with thread remains stationary in the absence of any outside force. Then gradually we bring another balloon near to this balloon. It is found that the balloon hung with a thread tried to go away from the other balloon. These two experiments are an indication to show that the comb is able to attract the paper pieces because they have equal and opposite charges. The charged up balloons on the other hand are repelling each other because both the balloons are like charges. This experiment helps in proving; i. The existence of electrostatic charge. ii. The coulomb’s law, which states, “Like charges repel each other and opposite charges attract each other”. Experiment-3 Students are asked to charge a Perspex rod by rubbing it with a silk cloth. The rod is placed on a watch glass. Then another rod is charged by rubbing with the silk cloth. When we try to take the second rod near to the first one, it is found that the rod on the watch glass starts nudging away. Important: This experiment shows how the rods get charged, while the ordinary silk cloth is acting as a charger. Experiment-4 Two ebonite rods are charged in similar manner by rubbing them with a woollen cloth. It is also found that the charged rods tend to repel each other. Experiment-5 Now the students are asked to bring one charged Ebonite rod near to another charged Perspex rod. It is found that the rods are now attracting each other. Important: 1. The charge appearing on rod after rubbing it with wool is called ‘negative’ 2. The charge appearing on the rod after rubbing it with silk is ‘positive’ charge. CLOSURE 10-15 minutes Students are told about how the charging takes place, when some amount of charge is transferred from one substance to another. Citing the example of rod and wool, it is told that initially both the substances were neutral. But during the process of rubbing, some negatively charged electrons are transferred from wool to the rod. Thus the rod becomes negatively charged, while the wool after shedding some negative electrons, becomes positively charged. It needs to be further emphasised that during all these experiments, no creation or destruction of charge is taking place. Instead the charge is being transferred from one substance to another. This is the all important law of conservation of electric charge. As per the law, ‘The total electrical charge in the universe remains constant’. Learning i. Principles of forces ii. Similar Charges tend to repel each other while opposite charges tend to attract each other. iii. Materials like woollen cloths, silk cloths has the tendency to bring up electrostatic charge iv. Learning science is fun and we can learn the scientific principles, provided we are keen observers of our surroundings It is worthwhile here to mention that while the students are able to learn the theoretical part of the law, they must also be told about the exact value of the charge in an electron and numerical calculations involved in the process. EVALUATION After the simple experiments, the students will be able to learn; The Coulomb’s law. How to calculate the amount of charge, if provided some related values. Interpretation of some of the ‘unusual’ activities involving the static charge Differentiating, to some extent, between the forces of attraction and repulsion The measure of intuitiveness amongst the students can be gauged from the manner in which they start involving themselves in informal discussions and sharing their experiences about such incidents. This goes a long way in preparing them for future. LESSON-2: Van de Graff Generator LESSON OBJECTIVES: 1. Further exploring the electrostatic Force around us 2. Efforts to mould the orientation of some of the students towards undertaking deeper studies in the subject 3. Understanding the difference between extremely high voltages and currents KEY CONCEPTS/IDEAS: 1. Generation/ transfer of charge 2. High Voltages 3. Low currents 4. Concept of Earthing SYLLABUS LINK: Prescribed Focus Area (PFA) Electrostatic Force and its effect on our life Knowledge and Understanding It requires; A basic understanding of the concept of electrostatic force Idea about voltages and currents Skills i. Readiness to experiment ii. Skills for conducting experiments Values and Attitudes iv. Inquisitiveness v. Patience during the experiments vi. Disciplinary attitude and temperament to follow the instructions PLAN: TIME TEACHER ACTION STUDENT-CENTRED ACTIVITIES (including assessment of learning) RESOURCES OPENING (About 10-15 minutes) Teacher takes them to the laboratory or to the room where Van Der Graff Generator is kept and tells them about some of the features of the Generator. For example some of the important features about the experiment are; i. The Van Der Graff is not a generator in strictest possible sense. It is instead a simple equipment in which the negative charges are transferred to the top, where these charges get accumulated. i. Students will be told to identify the components being used for making the generator. ii. As a learning exercise, the students can be told to devise a van de Graff generator themselves using some simple objects like; A soda can A small nail A small DC motor Batteries to run the motor A battery holder Dry pieces of paper A ready-made Van De Graff generator or the items required for constructing one. Quality Time Black-Board Marker Insulation tape After calling the rolls, the teacher would call upon the students to narrate whatever they’ve learnt so far. iii. Students will be told about the design and components of a typical Van De Graff generator iv. Demonstration of the functioning and accumulation of charge by Van De Graff generator. v. A typical and one of the favourite demonstrations of the functioning of this generator is to make someone’s hair stand on end. A flat and wide rubber band (e.g. a piece of surgical tube) to function as a belt for carrying charges from one end to other. Electrical wires Pieces of PVC pipe PVC coupler A PVC T-Connector Insulation tape A block of wood to function as insulation from earthing Pieces of fine metal wires (e.g. pieces of wire mesh) to function as brushes MAIN BODY Students will be told briefly about the history of the Van De Graff generator. Students will be encouraged to do the experiments individually. (35-40 Minutes) It was the work of Dr. Robert J. Van de Graaff, a professor at MIT. Developed in 1931, it was originally used as a research tool for atom smashing and high-energy X-ray experiments. This device is also known as a ‘constant current’ electrostatic device, because when we put a load on the generator its amperage remains the same. It is only the voltage which varies with the load. Therefore when we put a load on it i.e. we put our hands on the outer sphere of the generator, its voltage sharply decreases, but the current remains the same. On the other hand, batteries are known as ‘constant voltage’ devices, because in batteries the current varies when we put a load on it. For example we use batteries in our cars. When multiple loads like headlight, windshield wipers etc. are applied on the battery, its voltage remains the same, but current varies. That’s why there is no significant effect on the headlight, even if we turn on the wipers or turn on indicator lights etc. It needs to be emphasised here that the Van De Graff generator can generate voltages of hundreds of thousands of volts. It might appear startling on the first glance, but it doesn’t represent a serious shock hazard, because the current is very small. Before the experiment is undertaken, students should be able to recollect the theory part of the electrostatic energy. Students should also be asked about their knowledge about the positive and negative charged atoms and their properties. Though we will be using small current batteries for the experiment, but precaution need be taken to see that when the DC is turned on, the set up is firmly holding on to the ground, and there are not many vibrations or jerks. This could result in damage to the set-up or minor injuries to the persons standing near the equipment. CLOSURE 10-15 minutes Students are told about how the concentration of charges has taken place in the top dome of the Van De Graff generator. Normally a neutral material is used for the rollers along the route of the belt, but often it helps to take some materials which can help in doubling our efforts. For example in devising the upper roller, if it happens to be a neutral material, it helps the belt in discharging the positively charged ions towards the upper dome or sphere. But if the material happens to be made up of positively charged material like nylon, it helps in optimum discharge of positively charged ions and the belt in turn becomes more negative. Learning The properties of positive and negatively charges More about electrostatic energy Difference in voltage and current EVALUATION After undertaking this Van De Graff experiment, the students will be able to learn; The process of separation of charges Construction of Van De Graff generator Differentiation between voltage and current and how is it that we experience shock when we touch the wire in our domestic electric wiring (with 110-250 volts), but we don’t feel the shock, when we touch something at a voltage of about 70,000 volts. And of course the students will be able to share the ‘hair raising’ experiences with the fellow students, which will certainly help the cause of science teaching. Report Explaining ‘How the Two Lessons Address and Assess Student Conceptual Understanding of the Electrostatic Force There was a time when hydrogen atom was considered as the smallest elementary particle on earth. It was considered unbreakable. But as the technology developed and in-depth research took place, it has become known that the atom can further be broken into a number of other smaller particles. These charges are bound together by way of their polarity/ charge and a number of other natural phenomenons. Electrostatic force is one such force which binds the electrons in the orbit, within an atom. Though the concept is quite easy but it is found that the students often find it tough to ‘memorise’ the whole concept. Science and scientific concepts provide us the factual information about the manner in which a number of activities take place. But, the fear of long equations and lengthy theories often puts off the students and they tend to lose interest in the learning of science. This is bound to happen if we enter a class with the notion that we’ve to complete the syllabus and the students have to learn the topics. Bullock and Wikeley (2008) state that ‘individual educational relationships between students and a tutor are the key to effective learning’. Therefore, in order to make science learning a fun we need to; i. Provide examples which we often come across, but somehow we miss the science behind the happening of those actions. For example we might start from simple things like, why we are able to run on a rough surface, but find difficulty in running on a slippery surface; or why is it that when we drop a pencil, it goes down and doesn’t go up etc. ii. Encourage students to explore the answers and come out with their own sets of queries or examples involving science. Though students are reluctant to volunteer for assessing their strengths, as is rightly pointed out by Bailin et al. (1999). But teacher a successful teacher will have to help them in coming out of their shell. iii. Make it interactive. If Science teaching happens to be interactive, the learning becomes equally easy iv. Hold the attention of the class. Science teaching not only involves imparting factual information, but it also involves holding the attention of the students. These two lessons are intended to tell the students about the electrostatic force. This is the kind of force which we often come across but seldom realise the science behind it. The lessons have been designed in such a manner that the process of learning becomes more of the process of acquisition of knowledge, sharing of experience. Bloom (1964) said learning can take place in three types of approaches, namely cognitive, affective, and psychomotor. While traditional education had emphasis on cognitive approach. Today the emphasis is on psychomotor mode, which includes skills, abilities and competencies. Through this lesson it can be achieved when; i. We try to place before the students some of the examples which might appear trivial in nature, but when students come to know that these very things can help in generating voltages upto 70,000 volts, they are bound to become curious to know more. ii. Discoveries of science have often taken place not by design but by chance. For example, when Newton was sitting underneath an apple tree, an apple dropped over his head. He started wondering how is it that the apple is coming down to earth and not going upward. Thus he went to explain the concept of gravitational force. iii. In this lesson plan I have explained couple of easy examples which are bound to make the students think about their own experiences, which in turn would lead to efforts in correlating the things. iv. Once the level of interest and curiosity intensifies the established theories and principles like Coulomb’s law, bits of atomic structure etc. can be explained to the students. v. The learning is bound to become more interactive when the students are able to experience first-hand magic of electrostatic force by way of examples like the charge on a comb, Perspex rod, ebonite rod, balloons etc. vi. These are the examples which the students can easily share with their friends and family members as well. And while explaining the reason to their family and friends, they are bound to gain more confidence and theoretical knowledge. vii. The process of learning doesn’t become monotonous, during the period of this class because students will themselves be able to take turns in conducting the experiments. viii. The construction and explanation of Van De Graff generator will prove to be another good experience for the students. Thus far the word ‘Generator’ is supposed to have connotations of something very difficult, being manufactured in big production facilities. But once we are able to explain the making of Van De Graff generator to the students, they are bound to find it interesting. ix. After the students see the functioning of the Generator, things are bound to become more interesting of the entire class. x. All this while what is required is innovation and impromptu approach on the part of the teacher in dealing with students and responding to their queries. Concept Map Concept maps are basically meant to provide an idea about our vision in resolving some issues. For this lesson plan, the concept map could be as explained below; References: 1. Bullock, Kate and Wikeley, Felicity (2008). ‘Every child should have one: what it means to be a learning guide’. Improving Schools 2008; 11; 49. Sage Publication 2. Bailin, S., Case, R., Coombs, J. R. & Daniels, L. B. (1999) Common misconceptions of critical thinking. Journal of Curriculum Studies, 31(3), 269–83. 3. Bloom, B. S. et al. (1964), Taxonomy of Educational Objectives, Vol. 2, David McKay, New York, NY. Read More