static electricity. what is static electricity the buildup of electrical charges in one place....
Post on 15-Dec-2015
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Static Electricity Slide 2 What is Static Electricity The buildup of electrical charges in one place. Static = charge does not move or flow (usually a temporary condition). Can be detected by an electroscope. Slide 3 Examples of static electricity: Rubbing a balloon on your hair Walking across carpet Clothes tumbling in dryer What do these have in common? Friction!!!! Slide 4 Creating Static Charges Static charges result when some charges are transferred from one object to another by friction Which charges are easily removed? Recall structure of the atom. Slide 5 Recall from Chemistry Electrons (-) are on the outside of the atom so they can be easily removed, while protons (+) are held firmly in the nucleus Protons & Neutrons Electrons Slide 6 Two Types of Charge Electrons can be transferred by friction, but protons cannot Transferring protons would create a new element! LOSING electrons gives an object a POSITIVE charge GAINING electrons gives an object a NEGATIVE charge NOTE: When one object loses, another must gain - electrons cant be created or destroyed Slide 7 Combing transfers electrons from the hair to the comb by friction, resulting in a negative charge on the comb and a positive charge on the hair. BEFORE AFTER Slide 8 Induced charge Charged and neutral objects (not touching) are attracted because electrons move in the neutral object. Electrons move toward a +ve charged object and away from a ve charged one. This is called induced charge Slide 9 Conduction Conduction = direct transfer of charge Eg: walk across carpet and touch a doorknob shocking! Electrons are stripped from the carpet and you gain a net ve charge When you touch the doorknob, electrons jump onto it electrical discharge Slide 10 Slide 11 AttractRepelNeither +ve and -ve +ve and neutral +ve and +ve -ve and neutral -ve and ve Neutral and neutral Place an X in the appropriate box: Slide 12 AttractRepelNeither +ve and -ve X +ve and neutral X +ve and +ve X -ve and neutral X -ve and ve X Neutral and neutral X Place an X in the appropriate box: Slide 13 Rules of static electricity 1.Objects with like charges repel, but objects with unlike charges attract 2.Charged objects attract neutral objects Slide 14 Does friction always create static charge? Different materials have different strength of attraction for electrons If two objects of the same material are rubbed, no static charge forms (equal number of electrons transfer each way) Slide 15 If two different objects are rubbed, they have different attractions to the e- The stronger one will take e- away from weaker one and static charges build up Slide 16 Uses of static electricity Trapping particles in smokestacks of factories Applying grit to sandpaper Spray painting mesh (e.g. chain link fence) Powder coating Slide 17 The leaves are repelled by the like charge upon them. Slide 18 7.2 Electric Force--Summary Force is a push or pull - electric force can do both, without touching the object - it is an action-at-a-distance force. Laws of Static Charge Like charges repel Opposite charges attract Neutral objects are attracted to charged objects See pages 258 - 259 Slide 19 Charging Objects Charging By Conduction Charging through direct contact Extra electrons will move to a location where there is less of them Charging By Induction Bringing a charged object nearby a neutral object will cause charge movement and separation in the in the neutral object (like charges repel!) See pages 259 - 260 Slide 20