Description:

Lightweight pith balls help to show electrostatic attraction and repulsion.

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Magnetic Wires

Eddy Currents

Possible Incorporate Topics:

• Positive and Negative Charge
• Electrons and Electrostatics
• Attraction and Repulsion

Theory:

'pith\ n 1a: a usu. continuous central strand of spongy tissue in the stems of most vascular plants that prob. functions cheifly in storage.

 A pith ball is a very small, lightweight object that picks up electric charge quite well. A charged pith ball works well to show the Coulomb force between two charged objects. If a glass rod is rubbed with silk, the silk rubs some electrons off the rod. The rod thus becomes positively charged. Figure 1: Charging a glass rod Touching the positively-charged rod to two pith ball gives the balls each a small positive charge. Since like charges repel, the pith balls repel one another Figure 2: Charging the pith balls If an ebonite rod is rubbed with fur, the rod rubs some electrons off the fur. The rod thus becomes negatively charged and attracts the positively-charged pith balls. Figure 3: Charging a ebonite rod

Apparatus:

• Two pith balls hung by string
• A glass rod
• An ebonite rod
• A piece of fur and a piece of silk cloth
•

Procedure:

1. Charge up the glass rod with the silk rod first. Then touch both pith balls with the rod. The two balls should now repel one another.
2. Next, charge the ebonite rod with the fur. Bring the rod close to the balls. You will see the positively-charged balls are attracted to the rod.

+5 #12 Rhythm 2013-01-25 11:09
pith ball is an insulator so how can it acquire net positive charge???

+1 #11 roshan 2013-01-24 22:01
y only silk wire is used to hang pith ball electroscope

+4 #10 Ankita 2013-01-22 01:33

0 #9 Saphira 2013-01-08 22:10
The same thing but with one pith ball? Everyone says that a negatively charged object touches the neutral pith ball, and then say that an object is negatively charged. Could someone tell me which object becomes negatively charged?

+2 #8 Mukul Gupta 2013-01-04 10:59
How to estimate the charge induced on each of the pith ball using coulomb's law???

+2 #7 Skoller_89.warlord 2012-12-19 12:18
this Deduction was very Insightful and Exciting. =)

+4 #6 ammu 2012-12-04 01:12
What would be the approx charge induced on the ball???

+2 #5 Dr. Mike 2012-09-07 13:44
Quoting Emma:
What would happen if the pith balls had a neutral charge to a negative ebonite rod ?

As long as there is a charge difference, you should see an effect.

+3 #4 Emma 2012-09-07 12:38
What would happen if the pith balls had a neutral charge to a negative ebonite rod ?

+6 #3 Aman 2012-02-21 20:54
the diagram with the ebonite rod touching the pith balls is kinda wrong because protona dont move so yeah... other than that its fine :)