10.1 Exploring the Nature of Static Electricity

Transcription

1 10.1 Exploring the Nature of Static Electricity static electricity is caused by electric charges: charged particles that exert an electric force on each other examples of static electricity: lightning, shock when touching a doorknob, crazy hair when you take off a wool sweater Electrically Charged Particles RECALL: protons have a positive (+) charge, neutrons have no (0) charge and electrons have (-) charge protons and neutrons are found in the nucleus Static Charges object can become charged when electrons move from one object to another static charge/static electricity: the electric charge that builds up on the surface of an object an object that has MORE ELECTRONS than protons is negatively charged an object that has MORE PROTONS than electrons is positively charged if a NEUTRAL object obtains MORE ELECTRONS is becomes negatively charged if a NEUTRAL object LOSES ELECTRONS it becomes positively charged Friction and the Movement of Electrons How do atoms lose or gain electrons to become electrically charged? one common cause of electron transfer is friction: when object rub against each other the force of friction causes one of the objects to lose electrons, and one to gain them electrons are never LOST they are simply TRANSFERRED both objects are neutral before they are rubbed against each other

2 Electron Affinity different substances have different abilities to hold on to electrons the tendency of a substance to hold on to the electrons is called electron affinity Table 10.1: Triboelectric Series (on the right) the higher than material on the list, the more it will LOSE electrons using this table you can determine which material will be positively charged and which will be negatively charged when you rub two of the objects together e.g. rub nylon and steel together: which will be negative and which will be positive? the nylon is MORE LIKELY to lose electrons (higher in the table) and therefore will become positive and the steel will gain those electrons, becoming negative Laws of Attraction and Repulsion The Law of Attraction: states that particles with opposite charges attract each other The Law of Repulsion: states that particles with like charges repel each other Coulombs when two charges objects are placed closer together, the attraction or repulsion increases and decreases as they are moved further apart the metric unit for electric charge is the coulomb, named after the scientist to discovered this phenomena 1 coulomb = 6.24x10 18 electrons added or removed from a neutral object HATE Electrical Insulators and Conductors conductivity: the ability of materials to allow electrons to move freely in them insulators: hold onto their electrons and do not allow them to move easily examples: wood, glass, plastic conductors: allow electrons to move freely examples: metals conduction: the movement or transmission of electrons through a substance fair conductors/semi-conductors: electrons move less freely than in conductors LOVE Water as a Conductor pure water is NOT a conductor, but most water has dissolved minerals in it, making it a semi-conductor this is why you do not want to be in a lake during a thunderstorm!

3

4 10.1 Exploring the Nature of Static Electricity static electricity is caused by electric charges: charged particles that exert an electric force on each other examples of static electricity: lightning, shock when touching a doorknob, crazy hair when you take off a wool sweater Electrically Charged Particles RECALL: protons have a positive (+) charge, neutrons have neutral (0) charge and electrons have negative (-) charge protons and neutrons are found in the nucleus Static Charges object can become charged when electrons move from one object to another static charge/static electricity: the electric charge that builds up on the surface of an object an object that has more electrons than protons is negatively charged an object that has more protons than electrons is positively charged if a NEUTRAL object obtains more electrons it becomes negatively charged if a NEUTRAL object loses electrons it becomes positively charged Friction and the Movement of Electrons How do atoms lose or gain electrons to become electrically charged? one common cause of electron transfer is friction: when object rub against each other the force of friction causes one of the objects to lose electrons, and one to gain them electrons are never lost completely they are simply transferred both objects are neutral before they are rubbed against each other

5 Electron Affinity different substances have different abilities to hold on to electrons the tendency of a substance to hold on to the electrons is called electron affinity Table 10.1: Triboelectric Series (on the right) the higher than material on the list, the more it will lose electrons using this table you can determine which material will be positively charged and which will be negatively charged when you rub them together (friction) e.g. rub nylon and steel together: which will be negative and which will be positive? nylon will want to lose electrons (+) and steel will gain electrons (-) HATE Laws of Attraction and Repulsion The Law of Attraction: states that particles with opposite charges attract each other The Law of Repulsion: states that particles with like charges repel each other Coulombs when two charged objects are placed closer together, the attraction or repulsion increases and decreases as they are moved further apart the metric unit for electric charge is the coulomb, named after the scientist to discovered this phenomena 1 coulomb = 6.24x10 18 electrons added or removed from a neutral object Electrical Insulators and Conductors conductivity: the ability of materials to allow electrons to move freely in them insulators: hold onto their electrons and do not allow them to move freely examples: wood, glass, plastic conductors: allow electrons to move freely examples: metals conduction: the movement or transmission of electrons through a substance fair conductors/semi-conductor: electrons move less freely than in conductors LOVE Water as a Conductor pure water is NOT a conductor, but most water has dissolved minerals in it, making it a semiconductor this is why you do not want to be in a lake during a thunderstorm!