2What Is Static Electricity? A stationary electrical charge that is built up on the surface of a material
3Two kinds of chargesAfter being rubbed, a plastic ruler can attract paper scraps.Ruler carries electric charge.It exerts electric force on paper.This charging method is called charging by friction.The interaction between static electric charges is called electrostatics.
4Where do charges come from? Matter is made up of atoms.+–Proton (positive charge)+neutron (neutral)electron (negative charge)–atomnucleus
5Where do charges come from? If electrons = protons neutralIf electrons > protons gaining electrons, negative chargeIf electrons < protons losing electrons, positive charge
7Where do charges come from? Rubbing materials does NOT create electric charges. It just transfers electrons from one material to the other.
8Where do charges come from? When a balloon rubs a piece of wool...electrons are pulled from the wool to the balloon.+––The balloon has more electrons than usual.woolThe balloon: – charged,The wool: +charged
9Insulators and conductors Insulators: materials that do NOT allow electrons to flow through them easily.Insulators can be easily charged by friction as the extra electrons gained CANNOT easily escape.
104 Insulators and conductors Conductors: materials that allow electrons to flow through them easily.Conductors CANNOT be easily charged by friction as the extra electrons gained can easily escape.
11Induction: The production of a charge in an uncharged body by bringing a charged object close to it When negatively charged rod is put near a metal can...electrons of the can are pushed away from the rod.-induced charges top of the can: positiveattraction+buttom of the can: negative& attraction > repulsion-metal canrepulsion
12Attraction of uncharged objects Similarly, when charged rod is close to paper scrap...molecules of paper align.- attraction between the rod and + charge > repulsion between the rod and - charge.attraction+–paperrepulsion
16Gas Station FiresCarol said a static gas pump fire is blamed for burning her daughter so badly she needed skin grafts on her legs.Carol had put the gas pump nozzle on automatic and re-entered her car to write a check. When her then-12-year-old daughter, wearing a sweater and jacket that may have created static electricity, reached for the nozzle, flames suddenly ignited her clothing.
17A balloon has a negative charge when rubbed by a woollen cloth. 1 If the balloon can attract some paper scraps, which of the following cannot be the charge of paper scraps?A Neutral B PositiveC Negative
18A balloon has a negative charge when rubbed by woollen cloth. 2 During rubbing, what have been transferred between the woollen cloth and the balloon?A Electrons B ProtonsC Neutrons
19How does a positively charged rod attract a neutral object? When a + charged rod is put near neutral object, ______________ is induced on the side of the object near the rod and _____________ is induced on the side away from the rod. The rod can attract the netural object because _________ between rod and – induced charge > the ________ between rod and + induced charge.negative chargepositive chargeattractionrepulsion
20Grounding What is grounding? An object is grounded when it is connected to the earth through a connecting wire.If a charged conductor is grounded, it will become neutral.
21Grounding b How does grounding occur? When we touch a metal ball of positive charge...++electrons flow from the earth to the metal ball to neutralize the metal ball.+++–Metal ball becomes neutral.
22Grounding How does grounding occur? Similarly, if the metal ball is of negative charge...––extra electrons flow from the metal ball to the earth and the ball becomes neutral.––––
23Why do gasoline tankers usually have metal chains at the back? When cars run, their tires and bodies are usually charged by _______. For gasoline tankers, if the accumulated charge is large enough, _______can be produced and _________ will occur if gasoline vapor is ignited. Those metal chains conduct the charge on the bodies of tankers to the _______ and avoid the danger.frictionsparksexplosionground
24Lightning kills more than 60 people and injures more than 400 people a year in the USone mile every five secondsabout 20,000 CVoltage of up to 1.2x108 volts
47Do NowWrite a paragraph about the cartoon. Tell what he is trying to do. Will it work and why? What do you think will happen? Use the following words, static electricity, lightning, electrons, positive and negative charges.