Methods of Electrostatic Charging PDF

Lesson 1.1 Methods of Electrostatic Charging General Physics 2 1/2 Science, Technology, Engineering, and Mathematics Spark! Have you ever got electrostatically shocked when you touch a cold metal bar in a mall? 2 Or witnessed a girl holding a van de Gr...

Lesson 1.1 Methods of Electrostatic Charging General Physics 2 1/2 Science, Technology, Engineering, and Mathematics Spark! Have you ever got electrostatically shocked when you touch a cold metal bar in a mall? 2 Or witnessed a girl holding a van de Graaf generator while the strands of her hair repel one another? 3 Have you ever wondered what causes lightning? 4 The electrical shock, hair strands repelling one another in a van de Graaff generator, and the production of lightning results from the movement of electrical charges. This lesson discusses the nature of electric charge and how they are transferred from one material to another. 5 How are electrical charges transferred from one material to another? 6  Learning Competencies At the end of the lesson, you should be able to do the following: Describe using a diagram charging by rubbing and charging by induction (STEM_GP12EMIIIa-1). Explain the role of electron transfer in electrostatic charging by rubbing (STEM_GP12EMIIIa-2). Describe experiments to show electrostatic charging by induction (STEM_GP12EMIIIa-3). 7  Learning Competencies At the end of the lesson, you should be able to do the following: State that there are positive and negative charges, and that charge is measured in coulombs (STEM_GP12EMIIIa-4). Predict charge distributions, and the resulting attraction or repulsion, in a system of charged insulators and conductors (STEM_GP12EMIIIa-5). 8  Learning Objectives At the end of the lesson, you should be able to do the following: Identify the two types of charges: positive and negative. Predict charge distributions, and the resulting attraction or repulsion, in a system of charged insulators and conductors. 9  Learning Objectives At the end of the lesson, you should be able to do the following: Explain how charging by rubbing and charging by induction takes place. State the law of conservation of charge. 10  Electrostatics Static electricity (or electricity at rest) is produced when there is an imbalanced of electrical charges. “Electricity” comes from the Greek word elektron which means amber. Amber is able to produce static electricity when rubbed with a cloth. 11  Electric Charge Benjamin Franklin carried out famous experiments involving flying kites during thunderstorms. Classified charges as either positive or negative. 12  Electric Charge JJ Thomson discovered negatively charged particles known as electrons Ernest Rutherford discovered positively charged particles known as protons Charges are measured in coulombs JJ Thomson (C). 13 Interaction of Charges Unlike charges attract. 14 Interaction of Charges Like charges repel. 15 Why can there still be an attractive force between a neutral object and a charged object? 16  Interaction of Charges Consider a neutral sphere containing the same positive and negative charges. 17  Interaction of Charges Charge separation occurs when an external charged sphere is placed near the neutral sphere. 18 Conductors and Insulators Conductors Insulators 19  Methods of Charging Structure of the Atom Atoms are made up of three subatomic particles namely: electrons, protons, and neutrons. 20  Methods of Charging Net Charge An object’s net charge is the sum of the number of electrons and protons. negatively positively neutral charged charged 21  Methods of Charging Charging by Friction Electrons are transferred when objects are rubbed against one another. 22 What type of charge is transferred from one material to another during charging by friction? 23 Between two objects which are being rubbed, how can you determine which will become negatively charged and which will become positively charged? 24 Methods of Charging Suppose you rub a silk cloth against a glass rod. 25  Methods of Charging Which became positively charged? Negatively charged? 26  Methods of Charging The chemical property of an atom to attract electrons itself is called electron affinity. The triboelectric series ranks materials based on their tendency to acquire charge. 27  Methods of Charging Charging by Conduction Also known as charging by contact. A charged object is touched to a conductor. 28  Methods of Charging Charging by Conduction Assume that the neutral sphere is a good conductor. 29  Methods of Charging Charging by Conduction Charge separation occurs when a negatively charged rod is placed near the sphere. 30  Methods of Charging Charging by Conduction Upon contact, some electrons move from the rod to the sphere. 31  Methods of Charging Charging by Conduction Upon separation, both the rod and the sphere obtains a negative charge. 32  Methods of Charging Charging by Conduction Can you explain charging by conduction when a positively charged rod is used instead? 33  Methods of Charging Charging by Induction 34  Methods of Charging Charging by Induction 35  Methods of Charging Charging by Induction 36  Methods of Charging Charging by Induction 37  Methods of Charging Charging by Induction 38  Conservation of Charge Law of Conservation of Charge It states that the algebraic sum of all the electric charges in any closed system is constant. 39  Conservation of Charge Law of Conservation of Charge How many positive and negative charges are there? 40  Check Your Understanding Write T if the statement is true and F if false. 1. There are three types of charges: positive, negative and neutral. 1. The only factor that affects the charge of objects when you rub them is their electronegativity. 1. It is possible that charges will not be conserved when you consider charging by induction experiment. 41  Let’s Sum It Up! There are two types of charges: positive and negative. Changes in charges are brought by the movement of negatively charged particles. Forces between charges can be either repulsive or attractive. Like charges attract and unlike charges repel. 42  Let’s Sum It Up! There are two methods of charging an object: charging by friction and charging by induction. ○ Charging by friction can happen when you rub two objects with unequal electronegativity. The object with higher electronegativity will be negatively charged and the other object with lower electronegativity will be positively charged. 43  Let’s Sum It Up! There are two methods of charging an object: charging by friction and charging by induction. ○ Charging by induction can happen due to induced charges. The charges in a conducting object can be rearranged with the presence of an external charged object. 44 Challenge Yourself Rubber rods charged by rubbing with cat fur repel each other. Glass rods charged by rubbing with silk repel each other. A rubber rod and a glass rod charged respectively as stated above attract each other. Explain how this happens. 45 Photo Credit Slide 3: Van de Graaff Generator - Science City - Calcutta 1997 016 by Biswarup Ganguly is licensed under CC BY 3.0 via Wikimedia Commons. 46 Bibliography Freedman, Roger A. and Young, Hugh D. Sears and Zemansky's University Physics with Modern Physics (13th ed). USA: Pearson Education, 2012. Homer, David and Bowen-Jones, Michael. Physics Oxford IB Diploma Programme. UK: Oxford University Press, 2014. Hewitt, Paul G. Conceptual Physics (11th ed). New York: Pearson Education, 2010. Sang, David, Graham, Jones, et.al. Cambridge International AS and A Level Physics Coursebook. UK: University Printing House, 2014. Young, Hugh D., Roger A. Freedman, and A. Lewis Ford. Sears and Zemansky’s University Physics with Modern Physics (13th ed). USA: Pearson Education, 2012. 47