Presentation on theme: "Chapter 11 Electricity Objectives: 1. Identify two forces that result from electric charges 2. Explain why objects attract and repel each other. 3."— Presentation transcript:
1 Chapter 11 ElectricityObjectives: 1. Identify two forces that result from electric charges2. Explain why objects attract and repel each other.3. Communicate how positively charged object can beused to determine the charge on another object.4. Infer how electric charges behave in everydaysituations
2 “ + “ charge “ – “ charge “NO” charge Review concerning Charge and ForceRecall that matter is made of atoms which containelectrons, protons and neutrons.“ + “ chargePROTONS -“ – “ chargeELECTRONS“NO” chargeNEUTRONS –
3 What do charged particles create? The positive and negative electric charges inobjects can produce a force between theobjects. If charges are opposite, they willcause objects to attract to each other. Ifcharges are alike the will cause objects torepel or push away from each other.
5 Like charges will repel each other FORCE OF REPULSION“-”“-”Like charges will repeleach other
6 ELECTRIC FIELD An electric field is a region surrounding a charged object.Strongest part offield is closest tothe charged areaWeakest part of fieldIs the area farthest awayfrom the charged object
7 Perhaps you have experienced this. When you drive close to a power line you may get some “static” on a carradio. What causes this?Power lineBecause there is an electric current flowing throughthe power line there is an “electric field” around theline. This electric field can cause “interference” onyour radio.
8 ELECTRICITY AND YOUYour body uses electric signals to communicate with the brain.If you touch something hot, the “-” charge inside the nerve cellchanges sending a signal along the nerve cell to the spinal cord,to your hand, telling it to drop the object.
9 11.2 STATIC ELECTRICITYObjectives:1. Identify three ways static charge can build up2. Explain what causes lightning.3. Compare electric conductors and insulators4. Infer why lightning can be dangerous
11 How does the person who “shocked” you become “charged” with electricity?First of all, you must understand that of the threeParticles that make up an atom, ONLY THE –e CANMOVE.When the person who “shocked” you rubbed theirfeet on the carpet electrons from the carpet weremoved to the person. This build up of electrons“jumped” from their finger to your ear.Static build-up is when electrons become overloadedon an object. Static means stationary or not moving.
12 FRICTION In this example the person (object) became “charged” by Can you think of other examples of causingstatic build-up (charging) by friction?
13 CONDUCTIONCharging by conduction occurs when electrons aretransferred from one material to another by direct contact--When the leaves of the electro-scope become loaded with electronsthey repel and separate.--- --------electroscopea device which detects an electricalcharge
14 INDUCTION - - - --- -- - - - - - --- - --- ----- - Charging by induction occurs when charges arerearranged without direct contact, the charged objectsimple comes close to another object.---- --------What has become “charged”?-The leaves of the electroscopeelectroscope
16 +_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+ When clouds are swirled around and blown together byturbulence in the upper atmosphere, there is a great dealof friction between the water molecules. This frictioncauses electrons to be jarred loose and eventually thereis a build-up of electrons within an area of the cloud.This is called “static build-up”. When this happens,lightning can occur in several ways:
17 The most common form of lightning + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _+ _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + __ _ +_ _ _+ _ _ ++ _ _ _ _ + _ _ __ _ + _ _ _ + _ __ _ + _ _ _ __ _ _ _ _ _ _ _ _ _ _ _One end of thecloud has more+ charges.The other end of thecloud has more – charges.The + - attraction betweenthe ends of the clouds causesa “static discharge”(lightning)resulting in a cloud which nowhas evenly distributed + & -charges.What happens now?Lightning within a singlecloud is called“St. Elmo’s Fire”
18 + _ + _ When the negative end of one cloud comes close to What will happen here?_ _ _ + __ + _ _ _ ++ _ _ ___ _ _ + __ + _ _ _ ++ _ _ __+ + + _ ++ _ + + ___+ + + _ ++ _ + + ___A charged cloudA second charged cloudWhere is the + - attraction?When the negative end of one cloud comes close tothe positive end on another cloud you will seelightning from one cloud to another.
19 + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ +_ How does one cloud “charge” another?_ _ _ + __ + _ _ _ ++ _ _ __+ _ + _ + _ + _ + _ + _ + _ + _ + _ + _ +__ _ + _ _ _ + _ _ + _ _ _ ++ + + _ ++ _ + + ___+ _ _ + _ + +__A charged cloudA neutral cloudWhen a charged object comes close to another object, thesecond object becomes charged by __________________.INDUCTIONWhat makes this happen?Like charges repel so when the end with a large number ofelectrons (-) comes close to the other cloud the electronsin the neutral cloud are repelled to the other end of thecloud causing it to have charged ends.
20 How does lightning strike things on the ground? _ + _ _ _ + _ _ _ _What happens?+ + + _ + + _ + + +A charged cloud_ + + _ + +A neutraltree with+ & - scatteredequally throughoutWhen the cloud gets close tothe tree the tree becomes chargedby induction. When the + / -attraction becomes great enoughthere is a static discharge ofelectrons to the tree._ _ _ _ _ +
21 Why is it unsafe to seek shelter under a tree during a storm? Lightning will try to find thefastest way to the ground. Thepeople under the tree become“charged” by induction just likethe tree does. As lightningtakes its path to the ground, itwill come out of the tree and tothe boys then to the ground._ + _ _ _ + _ _ _ _+ + + _ + + _ + + +A charged cloud+ + + _ + ++ + + _ ++ +_ _ _ ___
22 LIGHTNINGWILLKILL YOU DEAD!Don’t make someone cry.
24 CONDUCTORS - A material through which electric charges flow easily. Examples include most metals such as gold, silver, copper,aluminum and mercury. Non metals such as water and acidare also good conductors.NOTE: Pure water does not conduct electricity, it musthave some type of electrolyte or substance in it. Since thewater you use at home is not pure water, it is a goodconductor, it is wise to be careful when handling appliancesaround wet areas.
25 INSULATORS: Materials through which electric charges cannot move easily.Examples include wood, ceramic, rubber, glass and plastic.Note: you may have noticed that most wire to electricalappliances are coated with rubber or plastic.insulationwireIn an insulator, the atoms are not arranged in a mannerwhich will allow the electrons to move freely. Therefore,insulators are not capable of carrying electrical energy.
26 While drying, some clothes pick up a negative charge while SCIENCE AND YOUDo your clothes ever stick together when you take them of the dryer?While drying, some clothes pick up a negative charge whileothers keep a positive charge.Using your knowledge about charges what happens?Does your hair follow the comb or brush instead of lying flat?Using your knowledge about charges, explain what youthink happens to your hair.