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Question about how the electroscope works (if the leaves move closer or farther...

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sushi2011 | Student, Grade 10 | eNoter

Posted February 22, 2012 at 12:55 PM via web

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Question about how the electroscope works (if the leaves move closer or farther apart)?

Explain which way the leaves will move when a charged rod is brought near.

In the picture, the rod is negatively charged and is close to the sphere or ball on the electroscope. The leaves are positively charged. Which way will the leaves move?

If the leaves were negatively charged, then nothing really happens right (it will stay the same)?

I really really really don't get this and this part is stressing me out.... I would appreciate detailed explanations not real life examples (two guys pushing against each other acting like opposite charges, etc) because it just makes it confusing. Thank you for your help

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bandmanjoe | Middle School Teacher | (Level 1) Senior Educator

Posted February 23, 2012 at 11:18 AM (Answer #1)

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Well, let's start at the beginning.  An electroscope is a device that has two gold leaves hanging side by side.  These gold leaves are attached to a brass ball device that delivers electrical charge to the gold leaves.

Now, here is where you are probably getting confused.  Before any electrical charge is applied, the net force of the gold leaves is zero.  There are no positive charges, nor are there any negative charges.  Zero, nada, zip.  That's why they hang there, there is no charge in them at all.

When you apply an electical charge to the brass ball device, it delivers the charge, be it positive or negative (but usually negative) to the gold leaves.  Since each leaf contains a similar charge, the leaves repel each other.  Opposite charges attract, like charges repel.  Over time, the charges "leak" out into the air, and the gold leaves again relax and hang side by side because the charge has left them.

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