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class 12th physics investigatory project on to estimate the charge induced on each one of the two identical styrofoam balls suspended in a vertical plane by making use of coulomb's law

1. To estimate the charge induced on each one of the two
identical Styrofoam (or pith) balls suspended in a vertical
plane by making use of Coulomb's law.
Submitted by –Aradhya Agrawal
Submitted to –Mrs. Neeti Ravi Sharma Ma’am

2. This is to certify that Aradhya Agarwal of class 12th, Gwalior Glory High
School has completed her investigatory project on TO ESTIMATE THE
CHARGE INDUCED ON EACH ONE OF THE TWO IDENTICAL
STYROFOAM (OR PITH ) BALLS SUSPENDED IN A VERTICAL
PLANE BY MAKING USE OF COULOMB’S LAW under my
supervision. she has taken utmost care and sincerity to complete this project.
I certify that this project is up to my expectation and as per the latest guidelines
issued by the CBSE Delhi
Chemistry Teacher
Mrs. Neeti Ravi Sharma

3. Acknowledgment
As a student of class XII, I did this project as
a part of my studies entitled “To estimate the
charge induced on each one of the two identical
Styrofoam (or pith) balls suspended in a
vertical plane by making use of Coulomb's law". I
owe a deep sense of gratitude to my chemistry
teacher whose valuable advice and guidance help
me in doing this project from conception to
completion. At the same time,Ican’t forget to
express my thankfulness to the Principal of our
School for extending her generous patronage
and constant encouragement.
Finally, I am thankful to my parents for
helping me economically.
Aradhya Agrawal
XII-A

4. 1.Introduction
2.Apparatus Required
3.Procedure
4.Observations/Observation Table
5.Results
6.Bibliography
INDEX

5. •Thefundamentalconceptinelectrostaticsiselectricalcharge.We
knowthatrubbercomboncatfur-producesa“static”charge.
Thisprocessiscalledchargingbyfriction.
•Thechargedparticlespresentinuniverseareofthreekinds:
positive,negative,andneutral.
•Neutralparticlesdonotinteractwithelectricalforces.Charged
particlesexertelectricalandmagneticforcesoneachother,butif
thechargesarestationary,themutualforceisverysimpleinform
andisgivenbyCoulomb’sLaw:
The study of the Coulomb forces among arrangements of stationary charged
particles is called electrostatics. Coulomb’s Law describes three properties of
the electrical force:-
1)The force is inversely proportional to the square of the distance between
the charges, and is directed along the straight line that connects their
center.
2)The force is proportional to the product of the magnitude of the charges.
3)Two particles of the same charge exert a repulsive force on each other,
and two particles of opposite charge exert an attractive force on each
other.
Introduction
where F = electrical force
between any two stationary
charged particles with
charges q1 and q2(in coulomb)
r = separation between the
charges ( in meters)
k =constant of nature =9x109
Nm2/C2

6. •Mostofthecommonobjectswedealwithinthemacroscopic(human-sized)
worldareelectricallyneutral.Theyarecomposedofatomsthatconsistof
negativelychargedelectronsmovinginaroundapositivelychargednucleus.
Thetotalnegativechargeoftheelectronsisequaltothetotalpositivecharge
ofthenuclei,thereforetheentireobjecthavenonetelectricalcharge.When
wechargeamaterialbyfriction,wearetransferringsomeoftheelectrons
fromonematerialtoanother.
•Materialssuchasmetalsareconductors.Eachmetalatomcontributesoneor
twoelectronsthatcanmoverelativelyfreelythroughthematerial.conductor
willcarryanelectricalcurrent.Othermaterialssuchasglassareinsulators.
Theirelectronsareboundtightlyandcannotmove.Chargesticksonan
insulator,butdoesnotmovefreelythroughit.
•Aneutralparticleisnotaffectedbyelectricalforces.Chargedobjectswill
attractaneutralobjectbytheprocessofelectricalpolarization.For
example,ifanegativelychargedrodisbroughtclosetoanisolated,neutral
insulator,theelectronsintheatomsoftheinsulatorwillbepushedaway
fromthenegativerod,andthepositivenucleiwillbeattractedtowardthe
negativerod.Hence,rodhasinducedpolarisationintheinsulator,butits
netchargeisstillzero.
•Thepolarisationofchargeintheinsulatorissmall,butpositivechargeisa
bitclosertothenegativerod,anditsnegativechargeisabitfartheraway.
Thus,thepositivechargeisattractedtotherodmorestronglythanthe
negativechargehencethereisanoverallnetattraction.Ifthenegativerod
isbroughtnearanisolated,neutralconductor,theconductorwillalsobe
polarised.Intheconductor,electronsarefreetomovethroughthe
material,andsomeofthemarerepelledtotheoppositesurfaceofthe
conductor,leavingthesurfacenearthenegativerodwithanetpositive
charge.Theconductorhasbeenpolarised,andwillnowbeattractedtothe
chargedrod.Nowifweconnectaconductingwireoranyotherconducting
materialfromthepolarisedconductortotheground,weprovidea“path”
throughwhichtheelectronscanmove.Electronswillactuallymovealong
thispathtotheground.Ifthewireorpathissubsequentlydisconnected,
theconductorasawholeisleftwithanetpositivecharge.Theconductor
hasbeenchargedwithoutactuallybeingtouchedwiththechargedrod,and
itschargeisoppositethatoftherod.Thisprocedureiscalledchargingby
induction.

7. ✓Small size identical balls (pitch/
Styrofoamsoft plastic)
✓Physical balance or electronic balance
✓Half Meter Scale
✓Teflon/ Cotton thread
✓Small Stand
✓Glass rod (or plastic rod)
✓Silk cloth (or wool cloth)
Apparatus Required

8. 1.Measurethemass(m)ofeachofthetwoidenticalpithballs
usingaphysicalbalance.
2.Hangthetwoballsfromarigidsupportusinglightsilkor
cottonthreadsofsamelength‘l’.
3.Rubtheglassrodsilkclothtoinducechargeonit.
4.Nowtouchtheglassrodwithboththepithballstogetherso
thatequalchargeisinducedonboththeballs.
5.Whenleftfreely,thetwoballswillrepeleachother.
6.Measurethedistancebetweentheballswhenareatrest.
Notedownthedistance.
7.Tochangethechargeonball,takethirdunchargedballtouchit
toanyoneofthetwoballsandtakethethirdballaway,and
repeatstep4.
8.Takeotherunchargedballsuspendedwithotheruncharged4th
ballandtakethe4thballawayandrepeatstep4.
Procedure:

9. ❖Massofeachpithballs(m)=200gm.
❖Radiusoftheball(a)=0.2cm.
❖Lengthofthread(l)=100cm.
Observations:
OBSERVATIONTable:

10. Result:
LettheforcebetweentwostationarychargesbeF.
Theweightoftheballw=mg
Therestoringforceoneachball=mgsinθ
FromthediagramintherightintriangleABC,
Sinθ=x/2l
Letthechargeoneachballbeq
1
,q
2
andq
3
thenat
equilibrium,
mgsinθ=kq×q/X
2
Chargeonthepithball=√{(mgr
3
)/2kl}

11. Bibliography
❑Books.google.co.in
❑www.google.com
❑PhysicsNCERTclass12book