Certific
ate
This is to certify that the PHYSICS project titled
“To estimate the charge induced on each one of
the two identical Styrofoam (or pith) balls
suspended in the vertical plane by making use
of Coulomb’s Law”
has been successfully completed
by Vansh Patil of class 12th
‘D’,
SNBP International School, Morwadi, in the
partial fulfilment by Central Board of Secondary
Education (CBSE) leading to the award of the
annual examination of the year 2022 -2023.

ACKNOWLEDG
EMENT
“There are times when silence speak so much
louder than words of praise to only as good as
belittle a person, whose words do not express, but
only put a veneer over true feelings, which are of
gratitude at this point of time.”
I would like to express my sincere gratitude to my
physics teacher Miss Luna and Miss Ruchita, for
her vital support, guidance and encouragement,
without which this project would not have come

forth. I would also like to express my gratitude to
the other staff of the Department of Physics for
their support during the making of this project.
INDEX
1.Objective
2.Apparatus Required
3.Introduction
4.Theory
5.Circuit Diagram

6.Observations/Observati
on Table
7.Results
8.Applications
9.Bibliography
OBJECTIVE

To estimate the charge
induced on each of the
two identical Styrofoam
(or pith) balls suspended
in a vertical plane by
making use of Coulomb’s
law.

Apparatus
Required
Small size identical
Styrofoam balls
Physical balance or
electronic balance
Meter Scale
Teflon thread
Stand
Glass rod (or plastic
rod)

Silk cloth (or wool
cloth)
Introduct
ion
The transformer is a device used for
converting a low alternating voltage
to a high alternating voltage or vice-
versa. A Transformer based on the
principle of mutual induction
according to this principle, the
amount of magnetic flux linked with
a coil changing, an e.m.f is induced

in the neighbouring coil. A
transformer is an electrical device
which is used for changing the A.C.
voltages. As such transformers are
built in an amazing strength of
sizes. In electronic, measurement
and control circuits, transformer
size may be so small that it weighs
only a few tens of grams where as
in high voltage power circuits, it
may weight hundreds of tones. In a
transformer, the electrical energy
transfer from one circuit to another
circuit takes place without the use
of moving parts. A transformer
which increases the voltages is
called a step-up transformer. A
transformer which decreases the
A.C. voltages is called a step-down
transformer. Transformer is,
therefore, an essential piece of
apparatus both for high and low
current circuits.

Theory
When an altering e.m.f. is supplied to
the primary coil p1p2, an alternating
current starts falling in it. The altering
current in the primary produces a
changing magnetic flux, which induces
altering voltage in the primary as well
as in the secondary. In a good
transformer, whole of the magnetic flux
linked with primary is also linked with
the secondary, and then the induced
e.m.f. induced in each turn of the
secondary is equal to that induced in
each turn of the primary. Thus, if Ep
and Es be the instantaneous values of
the e.m.f.'s induced in the primary and
the secondary and Np and Ns are the
no. of turns of the primary secondary
coils of the transformer and:

dΦ/dt= rate of change of flux in each
turnoff the coil at this instant, we have
Ep=-Np dΦ/dt ---------- (1)
And
Es=-Ns dΦ/dt ----------- (2)
Since the above relations are true at
every instant, so by dividing 2 by 1, we
get:
Es/Ep=-NS/Np -------- (3)
As Ep is the instantaneous value of
back e.m.f induced in the primary coil
p1, so the instantaneous current in
primary coil is due to the difference (E -
Ep) in the instantaneous values of the
applied and back e.m.f. further if Rp is
the resistance o, p1p2 coil, then the
instantaneous current Ip in the primary
coil is given by
IP= E-Ep/Rp
E-Ep = Ip Rp

When the resistance of the primary is
small, Rp Ip can be neglected so
therefore:
E-Ep = 0 or Ep = E
Thus, back e.m.f= input e.m.f
Hence equation 3 can be written as:
ES/Ep = Es/E = output e.m.f/ input e.m.f=
Ns/ Np =K Where K is constant, called
turn or transformation ratio.
Circuit
Diagram

Observati
on
Mass of Each Ball, (m)
= 200 gm.
Radius of the ball, (a) =
0.2 cm.
Length of thread (I) =
100 cm.

Results
 The output voltage of the
transformer across the
secondary coil depends upon
the ratio (Ns/Np) with respect
to the input voltage.
Sr. no. Charge on
Ball B1
Charge on
ball B2
Distance
between the
two balls (in
cm)
1 0.00𝜇𝐶 0.00𝜇𝐶 0.4cm
2 2.00𝜇𝐶 2.00𝜇𝐶 33.0cm
3 2.00𝜇𝐶 2.00𝜇𝐶 26.2cm
4 1.00𝜇𝐶 1.00𝜇𝐶 20.8cm

 The output voltage of the
transformer across the
secondary coil depends upon
the ratio (Ns/Np) with respect to
the input voltage.
 There is a loss of power
between input and output coil
of a transformer.

Applicati
ons of
Transform
ers
A transformer is used in almost all
a.c. operations:
 In voltage regulator for T.V.,
refrigerator, computer, air
conditioner, etc.
 A step-down transformer is used for
welding purposes.

 A step-down transformer is used for
obtaining large current.
 A step-up transformer is used for
the production of X-Rays and NEON
advertisement.
 Transformers are used in voltage
regulators and stabilized power
supplies.
 Transformers are used in the
transmissions of a.c. over long
distances.
 Small transformers are used in
Radio sets, telephones, loud
speakers and electric bells etc.

Bibliogra
phy
NCERT Chemistry
Academia.edu
Dokumen
YouTube