ELECTRICITY

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ELECTRICITY
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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.
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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
3) CHARGED OBJECTS ATTRACT NEUTRAL OBJECTS

2) OPPOSITE CHARGES ATTRACT
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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
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ELECTRON TRANSFER

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

ELECTROSTATIC SERIES

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

electrons transfer
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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
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INSULATORS AND CONDUCTORS
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

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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
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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.

• 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

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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.

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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)

1. 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
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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)