Pure Physics - Static Electricity

• qdtimes2

  11 Sep 09, 12:12

  Two light pith balls coated with aluminium are touched by a perspex rod. They will

  A. attract each other but be repelled by the rod

  B. attract each other but be attracted to the rod.

  C. repel each other but be attracted to the the rod

  D. repel each other and be repelled by the rod

   the ans is C, I know that they will get attracted to the rod but I don't know why the pith balls would repel each other. Thanks a lot !

• fudgester

  11 Sep 09, 12:18

  Because they were both charged up the same way, they would both have the same charges.

  Like charges repel.

• yiha093

  11 Sep 09, 15:24

  dude. u need to make ur question more clear

  eg. is the ball touching one another? position of rod ?

  best if got diagram !

• Audi

  11 Sep 09, 19:49

  Originally posted by fudgester:

  Because they were both charged up the same way, they would both have the same charges.

  Like charges repel.

  
  Yes, this explanation is exactly correctly.

  To make things simple. Initially you have the 2 neutrally charged balls. When you rub it with perspex rod, electrons will be transferred from the perspex to the balls, making perspex +ve charged and the balls -ve charged. Now you see, since balls and perspex have unlike charges, they attract. As both balls obtain -ve charges, they repel.

• yiha093

  11 Sep 09, 20:33

  Originally posted by Audi:

  
  Yes, this explanation is exactly correctly.

  To make things simple. Initially you have the 2 neutrally charged balls. When you rub it with perspex rod, electrons will be transferred from the perspex to the balls, making perspex +ve charged and the balls -ve charged. Now you see, since balls and perspex have unlike charges, they attract. As both balls obtain -ve charges, they repel.

  but if the ball touching each other then is different cause when being touched already.

  hence leading my to say the questions needs to be more clear?

• Audi

  11 Sep 09, 21:31

  Originally posted by yiha093:

  but if the ball touching each other then is different cause when being touched already.

  hence leading my to say the questions needs to be more clear?

  
  In the options, they already stated for you two of the possible outcomes. The question is very clear.

• qdtimes2

  11 Sep 09, 21:50

  the question is from a 2005 TYS book..at first i thought that it wasn't clear too.

  but since the pith balls are coated with aluminium, does that mean that electrons can be transferred from a non-metal object to a metal object by friction?

  thanks guys

• Audi

  12 Sep 09, 00:03

  Originally posted by qdtimes2:

  the question is from a 2005 TYS book..at first i thought that it wasn't clear too.

  but since the pith balls are coated with aluminium, does that mean that electrons can be transferred from a non-metal object to a metal object by friction?

  thanks guys

  
  Good question.

  You can refer to this site:

  http://www.phys.unt.edu/~klittler/demo_room/e&m_demos/5a20_20.html

  I don't really know how to explain this, but perhaps you'll understand better when you read this (it helps). As for the explicit explanation, perhaps somone else can help you out with that.

  Thanks

• yiha093

  12 Sep 09, 00:39

  link doesnt work. please attend to it. tyty
• qdtimes2

  12 Sep 09, 10:16

  try copying the link and pasting it to your browser's address