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Cell and Battery (Combination of Cells)
The Cell is a device which converts chemical energy in to electrical
energy. The cell is a form of stored or potential energy. Due to the property
of storing the cells are used as source of electrical energy in remote areas
and as backup source of electricity in developed places.
A cell consists of
a.
Positive Electrode or Cathode
b.
Negative Electrode and
c.
Electrolyte ( Chemical Solution)
Working of Cell
A Cell requires two metallic rods of different materials to make Positive
Electrode (Cathode) and Negative Electrode (Anode) and chemical solution
as electrolyte.
When we place any metallic rod in a
chemical solution (electrolyte); some
chemical reaction takes place between the
dipped rod and chemical solution. Due to
this chemical reaction some of the rod
atoms go into chemical solution as ions
while the remaining electrons create a
negative charge on the rod.
Similar chemical reaction also takes
place with another rod. As both rods are of
different metal, the tendency to lose ions is
different in different metals. Thus the
metallic rod which has greater tendency to
lose ions becomes more negative than
other metallic rod. This rod is called Negative Electrode or Anode.
Another rod, which has lesser
tendency to lose ions, is presumed as
Positive Electrode or Cathode. Due to
the difference in charge between two
electrodes a potential difference
develops between them.
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Cell and Battery (Combination of Cells)
When a wire connects the Positive and Negative Electrode (Cathode
and Anode) Electrons collect on the negative terminal starts flow from
Negative Electrode to Positive electrode as fast as they can. The flow of electron is
flow of electric current.
Categories and types of Cells
On the basis of used electrolyte the cells are also classified into two
categories
1. Wet Cells and
2. Dry Cells
Wet cell
A wet cell battery has a liquid electrolyte. This is also called as flooded cell
since the liquid covers all internal parts, or vented cell since gases produced
during operation can escape to the air. Wet cells are a precursor to dry cells
and are commonly used as a learning tool for electrochemistry.
The Wet cells may be primary cells (non-rechargeable) or secondary cells
(rechargeable). Originally all practical primary batteries such as the Daniell
cell were built as open-topped glass jar wet cells. Other primary wet cells
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Cell and Battery (Combination of Cells)
are the Leclanche cell, Grove cell, Bunsen
cell, Chromic acid cell, Clark cell and Weston
cell.
The Leclanche cell chemistry was adapted to
the first dry cells.
The Wet cells are still used in automobile
batteries and in industry for standby power
for switchgear, telecommunication or large
uninterruptible power supplies.
Dry cell
A dry cell has the electrolyte immobilized as a
paste, with only enough moisture in the paste to
allow current to flow. The dry cell can be used in
any position and will not spill its electrolyte if
inverted.
The structure of
Zinc- Carbon dry
cell is shown in
picture.
In this a cylindrical pot of Zinc works as
anode (Negative Electrode) and Carbon rod
placed in center works as cathode (Positive
Electrode) and paste of ammonium chloride
and manganese dioxide used as electrolyte.
On the basis of recharging the cell are classified into two broad categories,
each type with advantages and disadvantages.
1. Primary Cells and
2. Secondary Cells
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Cell and Battery (Combination of Cells)
Primary Cells
The Primary Cells can produce current immediately on assembly. These
batteries are intended to be used once and
discarded. The Primary cells provides electrical
energy by irreversible chemical reactions.
The Primary Cells can’t be recharged since the
chemical reactions are not easily reversible and active
materials may not return to their original forms, efforts of
recharging of Primary cell can be dangerous.
Common Dry cells (zinc-carbon batteries and alkaline
cells) that are used in flashlights and transistor radios
(e.g., AA cells, C cells) are good examples of primary cells.
Generally, these have higher energy densities than
rechargeable batteries.
Secondary Cells
The
Secondary
cells
are
also
called
rechargeable cells. The Secondary cells must
be charged before use; they are usually
assembled with active materials in the
discharged state.
The Rechargeable cells or secondary cells can
be used again and again by recharging.
The Secondary cells can be recharged by applying
electrical current, which reverses the chemical reactions
that occur during its use.
The Devices which is to recharge the Secondary cells are
called chargers or rechargers.
The oldest form of rechargeable battery is the lead-acid
battery. A common form of the lead-acid battery is the modern car battery
shown above in diagram.
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Cell and Battery (Combination of Cells)
Battery
The combination of two or more cells is called battery. We can combine the
cells as per our requirement but there are pre combined cells are also
available in market.
Two or more cells can combined in two basic combinations
1. Series Combination
2. Parallel Combination
Using these two combinations we can combine cells in a new combination
known as “Mixed Combination”.
Series Combination
When the two or more cells are connected in such a way that Positive
terminal of one cell gets
connected with Negative
terminal of another cell and
so on. The outer most
terminals of cells considers
as “Positive” and “Negative”
terminals of battery, as
shown in figure.
Properties of Series Combination of cells
In this combination the voltage of combined cells increases as the number of
combined cells increases. When two cells are combined the total voltage
becomes equal to
Total Voltage = Voltage of cell 1 + voltage of cell 2
VT = V1 + V2
The cells are combined in series connection to increase the output voltage.
Whenever a device of higher voltage is required to operate by cells the
series combination is only possible method of combination.
In Series combination of cells the current remains equal to the current rating
of single cell. So
Total Current = Current of cell 1= Current of Cell 2
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Cell and Battery (Combination of Cells)
IT = I1 = I2
The internal resistance increases in the series combination of cells.
RT= r1 + r2
If three Dry cell is of 1.5Volt are combined together in Series Combination.
Find the total effective or Output Voltage of supply source?
In Series Combination, the effective or total voltage of combined cells
becomes equal to the sum of voltage of all cell. Thus
VT=V1+V2+V3
So, VT= 1.5+1.5+1.5
VT= 4.5 Volt
Parallel Combination of cells
When the two or more cells are connected in such a way that Positive
terminal of one cell gets connected with
Positive terminal of another cell and
Negative
terminal
with
Negative
terminal.
The outer most terminals of each cell
remains connected with “Positive” and
“Negative” terminals of battery, as
shown in figure.
Properties of Parallel Combination of cells
In this type of cells combination the total voltage of combined cells remains
equal to the voltage of one cell.
i.e. Total Voltage = Voltage of Cell 1 = Voltage of cell 2
VT = V1 = V2
In this type of combination of cells the Total Current increases and becomes
equal to sum of current capacity of all connected cells. So the
Total Current = Current capacity of Cell 1 +Current Capacity of Cell 2
IT = i1 + i2
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Cell and Battery (Combination of Cells)
The cells are combined in Parallel connection to increase the current capacity
of supply without changing the Voltage. The cells are combined in Parallel
combination to provide current supply for longer period.
In this type of combination of cells the internal resistance of cells decreases.
1/RT= 1/r1 + 1/r2
If two pencil cells has been combined in Parallel Combination; find the total
Voltage?
In Parallel Combination the total Voltage remains equal to the voltage of
connected one cell (of highest Voltage).
The Voltage rating of a pencil cell is 1.5 Volt. So
VT=V1=V2
VT= 1.5 Volt=1.5Volt
VT= 1.5Volt
Mixed Combination
When we combined the cells using both basic types
of combination of cells, means series and parallel
both combinations are put together; the combination
is
called
“Mixed
Combination”.
The
Mixed
combination of cells developed to exploit the benefits
of both basic types of combinations.
Symbolic Representation of Cell
In Electrical Circuit the cell is represented by a symbol as shown in figure.
The symbolic diagram show the Positive and negative terminals
of cell.
The representation of two or more cells represents the battery.
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Cell and Battery (Combination of Cells)
Q1. What is the difference between Primary Cell and Secondary Cell?
Q2. What are the differences between Wet Cell and Dry Cell?
Q3. What is Electrolyte?
Q4. Write an example of Wet Secondary Cell commonly used in our home;
Draw physical diagram and label.
Q5. Draw and Write an example of Dry Secondary Cell, Draw physical
diagram and label.
Q6. Draw and Write an example of Dry Primary Cell, Draw physical diagram
and label.
Q7. You have a torch bulb working on 4.5 Volt supply. How many Cells of
1.5 Volt will be required to glow the bulb.
Q8. You will combine the cells in which type of combination and why?
Q9. Which type of cells/ battery is being used in Automobiles? Wet Cell/
battery or Dry Cell/ battery.
Q10. The used cells in automobiles are Primary or Secondary.
Q11. If Secondary battery is being used in automobile than explain the
method of its recharging.
Q12. Make an Observation Report of a Car/ Truck Battery.
Q13. Make a list of appliances available at your home works on Primary
cells.
Q14. Make a list of appliances available at your home works on Secondary
cells.
Q15. Identify the type of combination on the basis of symbolic diagram
Sl.No. Symbolic Diagram
Represents
1.
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Cell and Battery (Combination of Cells)
2.
3.
4.
5.
Q16. Mention the properties of combination of cells
Sl.No. Cell Combination
Properties
1.
2.
3.
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