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Sci 9 Lesson 1 April 28  - Static Charge
 

Sci 9 Lesson 1 April 28 - Static Charge

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  • Ask these questions and expect to get replies but don’t let it go on too long. Be encouraging if someone says something daft try and be positive.
  • Here’s my silly demo. The balloon will rub against the head and then pull away with the “hair” standing on end. You might need to explain what it’s supposed to be. The next few slides show what is happening to the charges. These should run automatically.
  • Re iterate that the head an balloon each started off with the same number of positive and negative charges but the rubbing moved charges onto the balloon and off the head. The balloon is now negatively charged and the head positively charged so that because opposites attract the hairs are attracted to the balloon

Sci 9 Lesson 1 April 28  - Static Charge Sci 9 Lesson 1 April 28 - Static Charge Presentation Transcript

  • Homework from last class:
    • Read Ch. 7.1 (pp. 248-254)
    • Complete the Charge It worksheet
    • Have you ever stuck a balloon to the wall after rubbing it on your head?
    • Has your sweater ever made crackling noises when you took it off?
    • Have you ever gotten an electric shock off your door knob?
    • Have you ever seen lightning?
  • All these things happen because of Static Electricity!
  • Chapter 7 pp. 248-254 Ch. 7.1 Static Charge
  • What is Static Charge?
    • Static charge (aka static electricity): an electric charge that can be collected and fixed in one place
    • ‘ static’ means stationary or not moving
    • Static electricity occurs when there is a build up of electric charge on the surface of a material.
    • ex: Objects rub against one another and transfer charge
    p. 248
  • Positive and Negative Charge
    • All matter is made of atoms
      • The centre consists of protons (positively charged) and neutrons (no charge)
      • Surrounding the nucleus are electrons (negatively charged)
    p. 250 electron proton neutron
  • Positive and Negative Charge
    • The movement , or transfer, of electrons from one atom to another changes the charge on the atom.
      • When electrons (-) are gained , the object becomes negative .
      • When electrons (-) are lost , the object becomes positive .
    Electrons are most often transferred through friction , when objects rub against each other. p. 250
  • The Amazing Balloon Static Demo!
  •  
  • + + + + + + + + + + - - - - - - - - - -
  • + + + + + + + + + + - - - - - - - - - -
  • + + + + + + + + + + - - - - - - - - - -
  • + + + + + + + + + + - - - - - - - - - -
  • + + + + + + + + + + - - - - - - - - - -
  • + + + + + + - - - - - - + - - - - + + +
  • Balloon Static Demo - Conclusion
    • The head and balloon each started off with the same number of positive and negative electrons , but the rubbing transferred electrons from the head onto the balloon.
    • Result: Balloon = negatively charged (-)
    • Head = positively charged (+)
    • The positively charged hairs are attracted to the negatively charged balloon , so the hair stands up .
    • The imbalance of positive and negative charges causes:
      • Balloons to stick to walls.
      • Hair to stand on end when you brush your hair on a dry day.
      • The electric shock you sometimes get from the door handle.
  • Insulators and Conductors
    • Electrical insulators: materials that do not allow electrons to move easily (Ex: glass, plastics, ceramics, and dry wood)
    • Electrical conductors: materials that allow electrons to travel freely (Ex: metals)
    • Only insulators are good at retaining static charge.
    • Coulomb (C): the unit of electric charge
    Charges on insulator Charges on conductor p. 252
  • Generating Static Charge
    • Van de Graaff generators (VDG): a device that uses friction to produce a large static charge on a metal dome.
    • As a rapidly moving belt moves over rollers, contact between the two results in a transfer of charge .
    • A moving belt produces
    • static charge on a metal
    • dome
    • The charge resulting on the
    • dome depends on the materials
    • used in the VDG belt and rollers.
    p. 253
    • Applications of Static Charge
    • Ex: electrostatic filters can be used to clean air, paint automobiles, and hold objects with electrostatic attraction.
    • Dangers of Static Charge
    • Ex: Built up static charge can discharge and cause serious shocks, explosions or fires (such as trucks that carry fuel)
    • Pumping flammables must ensure objects are grounded (connected to the Earth so that static charge is discharged).
    p. 253-254
  • Lightning rods protect buildings in the event of lightning by conducting lightning strikes through a grounded wire.
  • Time for everyone’s favourite scientist….Bill Nye!
  • Homework for next class:
    • Complete the “Conductors and Insulators” worksheet
    • Answer Check Your Understanding questions on
    • p. 257: Qs 1, 4, 5, 11, 13, 14, 15
    • Study for on time Ch. 7.1 quiz next class
    • Read over class notes and check class blog
    • http://www.msoonscience.blogspot.com
    • Have a great weekend!
  • Works Cited
    • Images taken from the following sources:
    • http://instant-art.com/store/index.php?main_page=product_info&cPath=1_84_87&products_id=7060
    • http://sdsta.k12.sd.us/SDAAPT/2007PhotoResults.htm
    • http://www.dak.com/reviews/3306story.cfm
    • http://jcooltech.webs.com/apps/photos/photo?photoid=100384418
    • http://startswithabang.com/?paged=8
    • http://www.chemistryland.com/CHM151W/10-LiquidsAndSolids/Chapter10.html
    • http://www.rfcafe.com/references/electrical/NEETS%20Modules/NEETS-Module-01-1-1-1-10.htm
    • http://www.cartuningcentral.com/how-to-paint-a-car
    • http://www.flickr.com/photos/ax2groin/566654614/
    • http://www.cartoonstock.com/directory/s/static_electricity_gifts.asp
    • http://www.wpclipart.com/household/outdoor/lightning_rod.png.html
    • http://www.tvrage.com/shows/id-2806