Electricity Introduction PDF

Electricity What is it? http://ed.ted.com/lessons/the-science-of-st atic-electricity-anuradha-bhagwat  Learning Goals for this Unit By the end of this unit I will… – LG1: Students are able to collect qualitative and quantitative data about the properties of static electric...

Electricity What is it? http://ed.ted.com/lessons/the-science-of-st atic-electricity-anuradha-bhagwat  Learning Goals for this Unit By the end of this unit I will… – LG1: Students are able to collect qualitative and quantitative data about the properties of static electricity through inquiry, to describe the relationship between them. – LG 2: Students are able to collect qualitative and quantitative data about the properties of current electricity through inquiry, to describe the relationship between them. – LG3: Students will use their critical thinking skills to assess the societal, environmental and economic impacts of electrical energy production and consumption. They will also quantitatively analyze static and current electricity. –  Physical Properties of Matter Electricity is related to the physical properties of matter. To understand electricity we must understand the structure of the atom. - - What sub-atomic + + particle can move in this solid? - - - + + +  Electricity A form of energy that results from the interaction of charged particles such as protons and electrons Bohr-Rutherford model of the atom All atoms contain electric charges What Element is this? (on your sheet)  Atoms Contain: Protons – positively charged + Neutrons – no charge (neutral) 0 Electrons – negatively charged – Most objects are electrically neutral because they contain equal numbers of positively charged protons and negatively charged electrons.  Recall: Atoms that have the same number of protons and electrons are neutral How many protons are there? How many electrons are there? Is this atom of Boron electrically neutral? YES!!!!!  Static Electricity – An imbalance of positively and negatively charged atoms. Electrons can jump from atom to atom releasing energy http://phet.colorado.edu/sims/html/john-trav oltage/latest/john-travoltage_en.html  Causes of Electric Charges When two neutral objects are rubbed against each other, electrons from the atoms in one material can move to the atoms in the other material Why do you think only the electrons move? Why don’t the protons or neutrons ever move?  One object GAINS ELECTRONS 🡪 now has overall negative charge  Gaining Electrons The substance has more electrons than protons. - - - - The substance gains + + a NEGATIVE charge - - - + + +  One object LOSES ELECTRONS 🡪 now has overall positive charge  Losing Electrons The substance has more protons than electrons. - - The substance gains + + a POSITIVE charge - - - + + +  Laws of Electric Charges or Laws of Electrostatic 1. Like charges repel ++ --  Laws of Electric Charges or Laws of Electrostatic 2. Unlike charges attract +-  Laws of Electric Charges or Laws of Electrostatic 3. Neutral objects are attracted to charged objects 0– 0+  Examples Rubbing a balloon on your hair causes e- to move from your hair (atoms) to the balloon (atoms) Negative charge Positive charge What’s my Charge?  Static Electricity Static electricity is an imbalance of electric charge on the surface of an object. “Static” means not moving.  How Static Electricity is formed? Static charges can be formed in one of three ways: 1) Friction 2) Contact 3) Induction  Charging by Friction When two objects are rubbed together electrons move from one object to the other, creating a charge on each object Different materials have different attractions for electrons To determine which object loses electrons and which object gains electrons use the electrostatic series  Electrostatic Series Different material’s atoms hold on to their electrons with different strengths Material Strength of hold on electrons When two substances Glass are rubbed together, Human Hair Weak one substance holds on Nylon to its electrons and the Wool other substance gives Fur up its electrons. Silk Therefore one Cotton substance becomes negatively charged and Rubber the other substance Polyester becomes positively Foam charged. Ebonite Strong Plastic Gold  Electrostatic Series Practice Problems: Work in pairs to see if you can determine Material Strength of hold on which substance in the electrons the following pairs Glass would have a negative charge: Human Hair Weak Nylon 1) Glass + Polyester Wool 2) Human hair + Fur Cotton Silk 3) Wool + plastic Cotton Rubber Complete this sheet Polyester Foam Ebonite Strong Plastic Gold Charging by Friction http://phet.colorado.edu/sims/html/balloons -and-static-electricity/latest/balloons-and-st atic-electricity_en.html  Experiment time You have been using the pHET simulations to look at the patterns with transferring of electrons. We have also just looked charging materials using Friction and examined the Electrostatic Series. Now lets collect some observations in a LAB. The handout is found here.  Second method of Charging: Charging by Contact Electric charge can be given to a neutral object by touching it with a charged object An object that has been charged by contact always receives the same charge as the one that is on the object that charges it!  Charging by Contact Transfer of electrons Before contact After contact During contact  Third Method of Charging: Charging by Induction When a charged object is brought close to a neutral object The charged object causes (induces) electrons in the neutral object to move The induced charge is OPPOSITE to the charge on the charged object  Charging by Induction Charged object Negative object Neutral brought NEAR object electroscope and INDUCES e- to move down into the 2 leaves Electroscope – a device for detecting the presence of an electric charge  Negatively charged rod attracts positive charges in the ball and e- move down to the leaves Leaves repel because of like charges Method of Creating Static Charges Summary Fill out your chart in the package.  Amount of Method of Initial Charge contact Final charge Electron charging on object between on objects Movement objects Charged object Electrons move unchanged. within the neutral One Neutral Opposite charge is object depending on Induction Object and one None temporarily induced the charge but are Charged object on the neutral not transferred object between objects. Static Electricity Safety The following two video clips show how dangerous static electricity can be for regular everyday activities. Please fill out the section on safety located on page 140 of the package.  In your package answer the following: If you are ever filling up a gas can for a lawn mower or other vehicle, how should you do this safely? Answer: Fill the canisters on the ground. Ground yourself as well.  Natural Electric Discharge What is an example of a natural electric discharge? Lightning What are the 3 ways lightning is caused by? the difference in charge between: a cloud and the ground, between two clouds, or between parts of a cloud. How does it happen? Build up of negative charge in the cloud and positive charge on the ground. Second Stage of Lightning Opposite charges attract, so the positive and negative charges are pulled toward each other. The electrons move down towards the ground because they are attracted by the positive charges on the ground Final Stage As soon as the protons and electrons connect the electrons travel down the cloud to the ground, showing the visible flash of light. Animated Steps for lightning strikes  Grade 9 summary lightning 1) In the cloud friction causes the changes in charge. Charged atoms of gases can move in the cloud. 2) This induces the opposite charge on the ground or closest object to the cloud. 3) When the charge difference is great enough, there is a discharge of electrons.  What about your car Richard Hammond (TopGear) demonstrates how a car can protect you from lightning. Conclusion: 3. Where is the safest place to be other than your home during a lightning storm and why? Video shows what a Faraday cage is and how we can use it. A Faraday cage is created anytime a space is enclosed by metal. It doesn’t have to be solid, it just haves to encompass an area around the space. This explains why Richard was safe in his car and how you can protect your car from thieves.  Uses of Static Electricity List three uses for static electricity? Removable signs, decals, stickers Filters that screen out sunlight Photocopiers Types of Materials  Conductors A material in which electrons CAN move easily from one atom to another Usually metals Examples: copper, aluminum  Insulators A material in which electrons CANNOT move easily from one atom to another Usually non-metals Examples: wood, paper, rubber, glass  Semi-Conductors Some non-metals (like Silicon) in which electrons can move fairly easily  What about Water? Is water a good insulator or conductor of electricity? Pure water is a good insulator, but most water contains dissolved substances that make it a good conductor. This is why you should NEVER use an electrical device near a body of water. If your radio fell into a bathtub while you were in it, the electric current would flow through the water into you! Why would firefighters spray mist on a fire involving electrical equipment? Why not use a stream of water? Grounding: Removing Static Charge – An object with a large number of charges – Can supply electrons to a positively charged object – Can remove electrons from a negatively charged object – Neutralizes the object – A conductor is grounded if electrons are free to flow between the conductor and earth