Electric Force

• Theory: When objects are rubbed against each other they acquire electric charge. Objects of the same electric charge attract and objects of opposite charges repel.
  
• Preliminary Setup
  • You need:
    • Scotch Tape, paper, glass bottle, soda can
    • You will be supplied with: plastic and wooden pieces; cotton, wool and silk cloth; teflon tube
  • Experimental setting:
    • Cut 4 pieces 15-cm-long scotch tape. Fold one end to prevent it from sticking.
    • Stick two pieces directly onto smooth surface. Write "X" on the folded end.(Both pieces are stuck on the table surface.)
    • Stick the third tape on the table as well. Write "B" on its folded end.
    • Stick the fourth tape on top of the "B" tape. Write "T" on its folded end.


• Activity 1: Determine how different objects interact through the electrostatic force.
  • Determine the interaction between the various scotch tapes.
    • Pull the two "X" pieces abruptly off the top of the table. Bring them close to each other.
      Do they repel or attract each other? Answer:
      Does it matter which side faces which side? Answer:
    • Pull the "T" and "B" pieces off the table together. Using both hands, separate the tapes abruptly. Bring them close to each other.
      Do they repel or attract each other? Answer:
      Does it matter which side faces which side? Answer:
  • Stick the "T" and the "B" tape to a surface, so that 10 or more cm of the tapes are hanging freely in the air. Make sure the tapes are sufficiently far so that they do not interfere with each other. At any time if you notice the tapes are beginning the loose their charge, you can recharge them by repeating the preliminary set-up.
  • For each of the following objects, determine whether they are repelled or attracted by tape "B" and tape "T". Record your data in your data table.

    Another "T" tape. Another "B" tape. "X" tape. Plastic rubbed with cotton. Wood rubbed with cotton. Wood rubbed with the blue paper towel. Teflon rubbed with fur/wool. Glass rubbed with silk. Baloon rubbed with cotton.

    A metal soda can. A paper sheet. Human hand. Two other materials of your choice. (Optional)

    
    
  • Record your data in the following table. Write down "attract" or "repel" according to your observations.
    
    

    Object	"T" tape	"B" tape
    "T" tape
    "B" tape
    "X" tape
    plastic rubbed with cotton
    wood rubbed with cotton
    wood rubbed with the blue towel
    wood rubbed with woold
    wool rubbed onto wood
    teflon rubbed with fur/wool
    glass rubbed with silk
    balloon rubbed with cotton
    soda can
    paper sheet
    human hand
    other:
    other:

  
  
  • Results.
    • Arrange the objects in two categories according to their charge.
      
      

      "T" charge	"B" charge

      
      
    • What is the charge of the soda can? Answer:
    • What is the charge of your hand? Answer: