Nov 26, 2014 Miss Mathieu STATIC CHARGES AND ENERGY

 Electricity  Static Charge (Static Electricity)  Charging by Friction  Electrostatic Series  Insulator  Conductor  Semiconductor  Ground KEY TERMS

 Electricity is a form of energy that results from the interaction of charged particles, such as electrons or protons  Static Charge an electric charge that tends to stay on the surface of an object, rather than flowing away quickly  Charging by Friction is a process in which objects made from different materials rub against ach other, producing a net static charge on each CHARGING BY FRICTION

 Most objects are electrically neutral – what does this mean?  One material has a stronger attraction to electrons (which are negatively charged) than another materials  The material with the stronger attraction pulls electrons off the material that has the weaker attraction WHAT HAPPENS WHEN OBJECTS ARE CHARGED BY FRICTION?

 Only electrons transfer because they have a small mass and are relatively far from the nucleus  Both materials become charged due to an EXCESS OR A DEFICIT of electrons

 Electrostatic Series is a list of materials that have been arranged according to their ability to hold on to electrons AN ELECTROSTATIC SERIES Materials with atoms that have a stronger hold on electrons become negatively charged Materials whose atoms have a weaker hold on electrons become positively charged Positive Negative

 An insulator is a material in which electrons cannot move easily from one atom to another  Each material in the electrostatic series on the previous slide is an insulator  A conductor is a material which electrons can move easily between atoms  A semiconductor is a material in which electrons can move fairly well between atoms  Conductivity refers to the degree to which electrons move between atoms INSULATORS & CONDUCTORS

 A Conductivity Tester is used to distinguish between an insulator and a conductor  Consists of: a battery connected to a light and two contact points  When the contact points touch a material that conducts electricity, electron flow through the light and the light goes on CONDUCTIVITY

 The simplest way to remove the net static charge on an object is to put it in contact with a ground  Ground an object that can supply a very large number of electrons to, or can remove a very large number of electrons from, a charged object, thus neutralizing the object  The earth is a fair conductor, but the earth’s capacity to absorb or supply electrons is so great that earth remains neutral when electrons are transferred between it and a charged object  You can ground many charged objects by touching them as your fingers conduct electrons. Your body can receive or supply enough electrons to allow for neutralization GROUNDING: REMOVING STATIC CHARGES

 When you comb your hair with a plastic comb, which object, the hair or the comb, holds on to its electrons more tightly? What is the charge on this object?  THE PLASTIC COMB  NEGATIVE CHARGE  If leather is rubbed with polyester, the polyester becomes negatively charged. Would you place leather above or below polyester in an electrostatic series?  BELOW CHECK FOR UNDERSTANDING

 Chapter 10  Section 10.1  Pages  Questions 1-8 HOMEWORK