mayank's presentation internal resistence of primary cell 1.doc
TRANSCRIPT
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
1/22
ACKNOWLEDGEMENT
I Shobhit Bansal Standard XII of science
section, St. Marys Inter College, Etawah is genuinely
thankful to my teachersMrs. Sarita Anil & Mr. Edwin T.J.
for their help and guidance which I received for the
completion of my ro!ect
INTERNAL RESISTANCE OF A PRIMARY CELL
I am also thankful to our rincipal, my colleagues "
parents who have always given me their support directly or
indirectly, which was of immense help towards the
completion of this pro!ect.
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
2/22
DECLARATION
I here#y declare that the pro!ect entitled
INTERNAL RESISTANCE OF A PRIMARY CELL$ is an originalwork done #y me during the year %&&'(%&&) under the
guidance " supervision of Mrs. Sarita Anil & Mr. Edwin
T.J..
Signature of *uide+ Shobhit Bansal
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
3/22
CERTIFICATE
his is to certify that the investigatory pro!ect
entitled -Internal Resistance of a Primary Cell$ is an riginalwork done #y Shobhit Bansalduring %&&'(%&&) under our
supervision " guidance.
lace+ St. Marys Inter College
Mrs. Sarita Anil
Mr. Edwin T.J.
/ate+
College Seal
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
4/22
INDEX
itle age 0o.
1. Introduction a2Electrochemical cells
%. rimary Cell
a2Simple 3oltaic Cell
#2/aniel Cell
c24eclaanche Cell
d2/ry Cell
5. Secondary Cells a24ead accumulator
#2Edison 6lkali Cell
7. 8utton Cell
'. 6dvantages of Secondary
Cell over a rimary Cell
). /isadvantages of Secondary Cell
9. Internal :esistance of Cell
;. Emf of a Cell
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
5/22
INTRODUCTION
In present scenario human life depends upon the newinvented technologies that will #ring ease to our life. ne such
important discovery was made in 1;th century and that was the
discovery of the -power of chemicals$ i.e. electrochemical cells.
ELECTROCHEMICAL CELLS
6 cell is a chemical electrical transducer, i.e. a device
which converts chemical energy into electric energy. 6
simple cell is composed of positive and negative electrode.
>hen cell is connected across the load of electric device,the potential drop takes place and device functions. his cell has
provided us a mo#ile source of electricity. Cells are of two types +
12 rimary cell via 4eclaanche cell, /aniel cell, Simple 3oltaic
cell and dry cell etc. and
%2 Secondary cell like 4ead acid accumulator, Edison cell, etc.
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
6/22
PRIMARY CELL
It is an electrochemical cell which once used cant #e put
to use again #y passing electric current.
rimary cell was accidentally discovered #y an Italian
professor -Luigi Galvani$. ?e o#served that when the nerves of a
freshly dissected frog was connected through copper and iron wire
the leg !erked violently. ?e concluded that it was due to animal
electricity in frogs leg.
4ater -Alessandro Volta$ modified his discovery anddeveloped Simple voltaic cell.
SIMPLE OLTAIC CELL
Constr!ction(
In simple voltaic cell dilute sulphuric acid work as
electrolyte. 6nd copper and @inc rod act as electrode of whichcopper rod is positive pole and @inc rod is negative pole.
ActionA
he dilute sulphuric acid dissociates as represented #elow+
?%S7 %?B B S7
%(
inc rod forms n%B as
n n%B B %e(
6s reaction proceeds concentration of n%B ion increases.
?B ions drift to the copper rod. n reaching the rod it takes an
electron " thus copper rod starts to acDuire the Bve charge due to
this potential difference set up #etween copper and @inc rod, the
ma=imum emf developed in voltaic cell is 1.&; 3.
"ANIEL CELL
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
7/22
It was developed #y -Danielin the year 1orking+
In the porous pot, @inc sulphate is formed. he reactions are A
n n%B B %e(
?%S7 %?B B S7
%(
n%B B S7%( nS7
n B ?%S7 nS7 B %?B B %e(
he formation of nS7on the porous pot does not affect
the working of cell. n diffusing out porous pot ? ions react with
copper sulphate solution.
%?B B CuS7 ?%S7 B Cu%B
6s the Cu%B ions deposit on the copper vessel it acDuire
positive charge. /ue to the development of this potentialdifference, it starts to give an emf of 1.1 3.
LECLAANCHE CELL
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
8/22
4eclaanche cell was invented #y -George De Leclaanche
in the year 1
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
9/22
It is a porta#le form of 4eclaanche cell.
Constr!ction$
In a dry cell a moist paste of ammonium chloride
containing @inc chloride is used as an electrolyte. inc chloride
#eing highly hydroscopic, it is added to ammonium chloride in
order to keep it moistened. he paste of 0?7Cl and nCl% is
contained in a small cylindrical @inc vessel, which acts as the
negative pole of the cell. 6 car#on rod fitted with a #rass cap isplaced in the middle of the @inc vessel. It acts as the positive pole
of the cell. he car#on rod is surrounded #y a closely packed
mi=ture of Mn% and charcoal powder in a muslin #ag while the
Mn% acts as depolariser, the charcoal powder reduces the internal
resistance of the cell #y making Mn% conducting. he @inc
container and its contents are sealed at the top with pitch or shell.
Action$
6 dry cell is only a modification of wet 4eclaanche cell.
herefore, the action of a dry cell as regards the chemical reactions
takes place are same as in the case of 4eclaanche cell.
he dry cells are manufactured in different si@es and shapes to suit
particular needs. Irrespective of the si@e of the cell, the emf of the
cell is nearly 1.' 3. Its internal resistance may vary from &.1 to
1& . Gurther an electric current of a#out &.%'6 can #e
continuously drawn from a dry cell.
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
10/22
SECON"ARY CELLS
6 secondary cell is one in which chemical energy is
converted into electrical energy #ut they do so only when they are
charged #y passing current through them #y some source.
hey are also called accumulators orstorage cells. hey are of two
types(
1.4ead acid cell or lead accumulator%.Edison alkali cell
LEA" ACC(M(LATOR
It is the most common type of storage #attery used in
automo#iles. It was invented #y Grench physicist, Gaston lantein
the year 1;'
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
11/22
"isc)ar'in'$
>hen the cell is connected to an e=ternal load circuit, it suchcurrent in the circuit and starts discharging . he dilute sulphuric
acid dissociates into ?B and S7%( ions.
?%S7 %?B B S7
%(
6t the negative plate+
# B S7%( B %e( #S7
6t the positive plate+
#% B %?B B %e( #B?%
# B?%S7 #S7B?%
#%B?%S7B%?B B %e( #S7 B %?%
C)ar'in'(In order to charge a lead accumulator, it is connected to a
#attery charger capa#le of supplying emf greater than that of thelead accumulator. >hile charging an accumulator,a high series
resistance is included in the circuit. he #attery charger make ?B
ions to move towards negative plate and S ions towards the
positive plate.
6t the negative plate+
#S7 B %?B B%e( # B ?%S7
6t the positve plate+
#S7 B S7%( ( %e( #% B %S5%S5 B %?% %?%S7#S7B %?% B S7
%(( %e( #%B%?%S7herefore, during the charging process, #S7 at#oth
lectrodes is connected #ack into spongy lead F#2 at negative plate
and #% at positive plate.
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
12/22
E"ISON AL*ALI CELL
It is also called nic!el"ironF#i"$e2 cell.
Constr!ction(
Its positive plate consists of a num#er of tu#es ofperforated steel ri##on #ound specially " held together #y steel
rings. he tu#es are nickel plated. he active material consists of
0iF?27 " flakes of metallic nickel are packed into the nickelplated steel tu#es in alternative layers.
he negative plate is made from finely perforated nickelled
steel strips, stamped into pockets. he pockets are filled with
powdered iron o=ide.
%OR*IN+(
he chemical changes during charging and dischargingcan #e represented #y the following reversi#le reaction+
0iF?27 B H? BGe 0iF?2% B H? B GeF?2%
he emf of the fully charged cell is 1.7'3 " it falls to1.%3 on discharge.
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
13/22
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
14/22
A-.anta'es of secon-ary cell o.er a /rimary cell #
1. Secondary cell can #e put to use again and again #y
recharging it. >hile a primary cell once discharged cannot
#e recharged.
%. he internal resistance of a secondary cell is less than that
of a primary cell. 6s such a secondary cell ena#les to draw
much larger current.
"isa-.anta'es of secon-ary cell #
1. 6 secondary cell has to #e charged first so as to o#tain
electric energy from it. In other words, secondary cell
reDuires a lot of time #efore it can #e put to use, while
primary cell stsrts functioning immediately after its
construction.
%. he initial cost of a secondary cell is Duite large as
compared to that of a primary cell.
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
15/22
INTERNAL RESISTANCE OF CELL
Internal resistance of a cell is defined as the
resistance offered #y the electrolyte and electrodes of a cell
when the electric current flows through it.
he value of internal resistance of a freshly prepared
cell is generally low and its value goes on increasing as the cell
is pur to more and more use.
his internal resistance has a negative effect on the
working of a cell, it reduces the efficiency of a cell.
he internal resistance of a cell depends on the following
factors+
1. /istance #etween the electrodes
%. he nature of the electrolytes
5. he nature of electrodes
7. 6rea of the electrodes immersed in the electrolyte. If area
increases, internal resistance decreases.
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
16/22
EMF of a Cell
Emf of a cell is defined as the potential difference
#etween the two electrodes of a cell in a closed circuit. It is
denoted #y 3.
>hen the electric cell is in the open circuit the
current flows through the circuit. here is a fall of potenteial due to
the internal resistance of the cell. he terminal potential difference
#etween the two electrodes of a cell is less than the emf of the cell
#y an amount eDual to potential drop due to the internal resistanceof the cell. hus, the terminal potential difference of cell is always
less than the emf of the cell.
3 E ( Ir
Consider a cell of emf E and internal resistance r
which is connected to e=ternal resistance :. 6 high voltage
voltmeter is connected across the electrode of cell. >hen key H is
closed, current flows and
otal resistance : B r
Magnitude of current, I EJ:Br
otential difference across internal resistance,Fr2 Ir
Grom hms law,
3 I:
3 FEJ:Br2:
r, r FE(3J32:
6ccoding to the definition of internal resistance,
3 E ( Ir
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
17/22
If I &, 3 E
he terminal potential difference across terminal of cell eDuals to
potential difference across e=ternal resistance.EXPERIMENT
O,0ECT$ To determine the internal resistance of a primary
cell using a potentiometer.
APPARAT(S $ 6 potentiometer, a #attery, two one(way keys, a
rheostat of low resistance, a galvanometer, a resistance #o=, a
!ockey, connecting wires and piece of sand paper.
THEORY $ he internal resistance of a primary cell is given #y A
r Fl1A l%2Jl% K :
?ere l1and l%are the #alancing lengths without shunt
and with shunt respectively and : is the shunt resistance.
PROCE"(RE$
1. /raw the circuit diagram.
%. Clean the ends of the connecting wires with the sand paper
and make tight connections.
5. ight the plugs of resistance #o=.
7. Check the emf of the #attery and cell, and see that emf
of the #attery is greater than the emf of the cell.'. ake minimum current from the #attery making rheostat
resistance @ero.o test the correctness of the
connections +F insert the plug in the key H and note the
reading. ake out %&&& resistance plug from the
resistance #o=2.
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
18/22
). o test the correctness of the connections F insert the plug
in the key H1" note the reading. ake out the %&&&
resistance plug from the resistance #o=29. >ithout inserting the plug in the key H%ad!ust the rheostat
so that a null point is o#tained on the fourth wire of the
potentiometer.
;. Introduce the %&&& plug #ack in its position in the
resistance #o= and #y slight ad!usting the key.
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
19/22
of the either of the two cells.
'. Current should #e passed for short time only, while
finding the null point.
). Cell should not #e distur#ed during e=periment.
SO(RCES OF ERROR #
1. he au=iliary #attery may not #e fully charged.
%. he potentiometer wire may not #e of uniform cross(
section and material density throughout its length.5. End resistances may not #e @ero.
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
20/22
BIBLIOGRAPHY
Modern(s a)c o' hsics Satish H. *upta
*om%rehensive ractical hsics L.0. Laiswal
*once%ts o' hsics +Vol.,- ?. C. 3erma
A Tet)oo! o' Electricit /. C. andey
and Magnetism
/. E. /rodov /. 8. Singh
radee%(s $undamental hsics H. 4. *om#er
H. 4. *ogia
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
21/22
-
8/10/2019 MAYANK'S PRESENTATION INTERNAL RESISTENCE OF PRIMARY CELL 1.doc
22/22