ELECTRICITY

STATIC ELECTRICITY

1) An atom can get a charge by gaining or losing electrons.

Review - On your handout, label the diagram and fill in the blanks.

2) An atom will become a negative ion if it gains electrons

3) An atom will become a positive ion if it loses electrons. +

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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

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2) OPPOSITE CHARGES ATTRACT

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3) CHARGED OBJECTS ATTRACT NEUTRAL OBJECTS

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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

STATIC ELECTRICITY - when charges build up on the surface of an object and tend to be stationary (static)

Ebonite Rod

Fur

• If we rub an ebonite rod with a piece of fur, both objects become charged.

Demonstrations:1)Pith ball2)Water stream3)Evaporating dish

• How do we know the charge on the ebonite rod?

ELECTRON TRANSFER

ELECTROSTATIC SERIES• this is a list of materials that have been arranged according to their ability to hold on to electrons

ELECTROSTATIC SERIES

AcetateGlassWoolFur, human hairCalcium, MagnesiumSilkAluminum, ZincCottonParaffin WaxEbonitePlastic (polyethylene)Carbon, Copper, NickelRubberSulfurPlatinum, gold

weak hold on electrons

strong hold on electrons

electronstransfer

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?

electronstransfer

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OPPOSITES ATTRACT = STATIC CLING

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INSULATORS AND CONDUCTORS

CONDUCTORS - a material in which electrons can move easily between atoms

INSULATORS - a material in which electrons cannot move easily between atoms

- metals (copper, iron)- have a weak hold on their outer electrons

- 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

extra electronsflow to ground

electrons flow from Earth toneutralizethe sweater

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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.

• Hair transfers electrons to balloon

• Hair is now positively charged

• Balloon is negatively charged

• negative balloon put against neutral wall• negative charges in wall are repelled by negative balloon• surface of wall is now positively charged

• Balloon is attracted to the wall

SEATWORK

• answer # 1, 3 on pg 406 in the textbook.• answer # 3, 4, 6 on pg 410 in the textbook.

HOMEWORK (Handout)

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 - 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)

3. 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

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)

SEATWORK