ELECTRICITY

Review - On your handout, label the diagram and fill in the blanks. STATIC ELECTRICITY Review - On your handout, label the diagram and fill in the blanks. + - 1) An atom can get a charge by gaining or losing electrons. 2) An atom will become a negative ion if it gains electrons 3) An atom will become a positive ion if it loses electrons.

+ + + - - - + - EXPLORING STATIC CHARGES ELECTRICITY - a form of energy that results from the interaction of charged particles (such as protons and electrons) LAW OF ELECTRIC CHARGES 1) LIKE CHARGES REPEL 3) CHARGED OBJECTS ATTRACT NEUTRAL OBJECTS + + + - - - 2) OPPOSITE CHARGES ATTRACT + -

STATIC ELECTRICITY when charges build up on the surface of an object and tend to be stationary (static) CHARGING BY FRICTION when two materials are rubbed together , the friction can cause electrons to get knocked off one material and transferred to the next If we rub an ebonite rod with a piece of fur, both objects become charged. Ebonite Rod Demonstrations: Pith ball Water stream Evaporating dish Fur

ELECTRON TRANSFER ELECTROSTATIC SERIES How do we know the charge on the ebonite rod? ELECTROSTATIC SERIES Acetate Glass Wool Fur, human hair Calcium, Magnesium Silk Aluminum, Zinc Cotton Paraffin Wax Ebonite Plastic (polyethylene) Carbon, Copper, Nickel Rubber Sulfur Platinum, gold weak hold on electrons strong hold on ELECTROSTATIC SERIES this is a list of materials that have been arranged according to their ability to hold on to electrons electrons transfer

- - - + + + OPPOSITES ATTRACT = STATIC CLING REAL LIFE SCENARIO You put some cotton socks in the dryer along with a wool sweater. When you pull them out of the dryer, the sock sticks to the sweater. Explain? - - + - + + electrons transfer OPPOSITES ATTRACT = STATIC CLING

INSULATORS AND CONDUCTORS a material in which electrons can move easily between atoms metals (copper, iron) have a weak hold on their outer electrons INSULATORS a material in which electrons cannot move easily between atoms non- metals (rubber, glass, plastic) have a strong hold on their outer electrons http://www.youtube.com/watch?v=Z69k-_USHc8&feature=PlayList&p=B66AC571BA680238&playnext=1&playnext_from=PL&index=14

GROUNDING when a charged object is discharged or neutralized by a connection with Earth Earth is so large it acts like a pool of charge - it can give or take electrons - but its always remains neutral - - - + - electrons flow from Earth to neutralize the sweater extra electrons flow to ground

CHARGED OBJECTS ATTRACTING NEUTRAL OBJECTS??? REAL LIFE SCENARIO You rub a plastic balloon on your head several times. You then put the balloon against a wall and it sticks. Explain. Balloon is negatively charged Hair transfers electrons to balloon Hair is now positively charged Balloon is attracted to the wall negative balloon put against neutral wall negative charges in wall are repelled by negative balloon surface of wall is now positively charged

SEATWORK Answer these questions on a separate sheet of paper. Use full sentences and be as thorough as possible. (Refer to pg 403 - 409 in textbook) How do anti-static sheets work for clothes? Why are static charges more common during the winter when the air is dry? HOMEWORK (Handout) answer # 1, 3 on pg 406 in the textbook. answer # 3, 4, 6 on pg 410 in the textbook.

HOMEWORK - pg 406 #1 , 3 1. The comb holds its electrons more tightly. The charge on the comb would be negative (its takes electrons from the hair) Leather loses electrons - polyester gains electrons (becomes negative), therefore leather has a weaker hold on its electrons and must be above polyester on the series. HOMEWORK - pg 410 #3, 4, 6 3. Aluminum is closer to human hair than plastic in the electrostatic series. Since aluminum and human hair are close, their hold on electrons are similar and the transfer of charge will be minimal. 4. Nylon - lose electrons - positively charged silk - gain electrons - negatively charged 6. a) X - neutral, Y - neutral, Z - neutral b) Cloth Y - it gained electrons, solid X lost electrons c) Solid Z gained electrons, stronger hold on electrons than cloth Strongest to weakest - Solid Z, Cloth Y, Solid X

SEATWORK ANTI-STATIC SHEETS Anti-static sheet is a small piece of cloth with a waxy compound Hot air vaporizes the wax and coats the clothes - causing the clothes to behave as if they were made up of the same material WHY IS STATIC MORE COMMON DURING WINTER THAN SUMMER? dry air is a good insulator, moist air is a fair conductor in summer, air is moist and charges can transfer to or from the water vapour in the air side note - pure water is a good insulator , water is almost never pure, so water is usually a good conductor of electricity (so get out of the pool during a thunderstorm)