Thales Greek who lived around 600 B.C.E. One of the first to describe phenomenon related to electricity Described what happened when rubbed a piece of amber with wool William Gilbert English scientist repeated Thales experiment in 1570 Named the effects electricity Electricity comes form the Greek word for amber, elektron Thales and Gilbert Discovered electricity is everywhere Electric Energy Energy: ability to do work or cause changes - stove converts electric energy into heat energy that cooks food - light bulb converts electric energy into light and heat energy Electric Charge Electrical charge is a force within the particle. Basic property of matter All matter is made up of atoms. 1
Atoms Everything in the universe is made of atoms The human body is made of atoms. Air and water are, too. Atoms are the building blocks of the universe. If you could see an atom, it would look a little like a tiny center of balls surrounded by giant invisible shells. Atoms are so small that millions of them would fit on the head of a pin. Atoms are made of even smaller particles. The center of an atom is called the nucleus. It is made of particles called protons and neutrons. The protons and neutrons are very small, but electrons are much, much smaller. 2
Electrons spin around the nucleus in shells a great distance from the nucleus. If the nucleus were the size of a tennis ball, the atom would be the size of the Empire State Building. Atoms are mostly empty space. If an atom were the size of Turner Field, the nucleus would be like a mosquito over second base. Protons, Electrons, & Neutrons Protons - have a positive charge (+) Electrons - have a negative charge (-) Neutrons - carry no charge number of neutrons can vary Electrical Charge Concentration of electric charges Law of Electric Charge Like Charges Repel Objects that have the same charge repel each other Object exerts a force on the other object Forces push objects apart 3
Law of Electric Charge Opposite Charges Attract Objects that have opposite charges are attracted to each other Object exerts a force on the other object Forces pull the objects together Static Charge Electrically neutral equal number of protons and electrons Static Charge Object has a positive or negative charge Neutral objects gains electrons, negatively charge Neutral objects loses electrons, positively charge Static Electricity Buildup of charge on an object Most static charges trillions times larger than charge of single electron or proton Examples:»Shock from touching doorknob after walking on carpet Comb and Paper Experiment Effect of static electricity when small pieces of paper were attracted to plastic comb after comb was rubbed with wool»lightning 4
FRICTION Objects can be charged by rubbing them together when two neutral objects rub together, electrons are transferred from one object to the other Example: Static Cling: as clothes tumble together in dryer some become positively charged and others negatively charged Charging by friction Gives two neutral materials opposite charges when rubbed together NO NEW CHARGES ARE CREATED Existing charges move to other objects or to new areas on the same object FRICTION - DEMONSTRATION Rubber rod that is rubbed against a piece of wool Electrons move from the wool to the rod Rod becomes negatively charged Wool becomes positively charged 5
FRICTION - DEMONSTRATION Rubbing a balloon on your hair electrons move from hair to the balloon balloon becomes negatively charged hair becomes positively charged Conduction Neutral objects can be charged by coming into contact with an already charged object when a charged object touches a neutral object, electrons are transferred to the neutral object objects that are charged by conduction have the same charge as the object that was used to charge them Charging by conduction Happens when electrons move from one object to another by direct contact NO NEW CHARGES ARE CREATED CONDUCTION - DEMONSTRATION Touch a negatively charged rubber rod to a pile of neutral paper confetti confetti quickly flies apart pieces of confetti gain electrons and become negatively charged like charges repel CONDUCTION - DEMONSTRATION A positively charged glass rod touches an uncharged metal rod electrons from the metal rod move to the glass rod the metal rod looses electrons and becomes positively charged Induction Charged object is brought close to a neutral conductor, electrons in the neutral conductor can move to the new positions A material has areas of both negative and positive charges Causes an object to have a charge that is opposite to the charge that is brought near it 6
Charging by induction Happens when charges in an uncharged object are rearranged without direct contact with a charged object INDUCTION - DEMONSTRATION Rub a balloon against someone s hair, charging the balloon by friction. The balloon becomes negatively charged. Hold the balloon near a neutral wall and let go. negative charge of the balloon induces a region of positive charge on the wall MISCONCEPTION ALERT!!!!!! MISCONCEPTION atoms can gain or lose protons as well as electrons TRUTH atoms can only lose or gain electrons, which are negatively charged A net loss of electrons leaves an atom positively charged A net gain of electrons leaves and atom negatively charged Conservation of Charge When you charge something by any method, no charges are created or destroyed The numbers of electrons and protons stay the same Electrons simply move from one atom to another Charges are neither created or destroyed, they are conserved Van de Graaff Generator Lightning 7
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