Battery - Batter y A battery is an Electrochemical cell or...

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Batter y A battery is an Electrochemical cell or often several electrochemical cells which are connected in series to produce a constant voltage to run portable goods. Mainly batteries are of three types: 1) Primary Battery is the one in which cell reactions are irreversible. E.g. Lechlanche cell, Zn-Carbon Battery. 2) Secondary Battery is the one in which cell reactions can be reversed by passing external emf in opposite direction. i.e. it can be used for many cycles of charging and discharging. E.g. Lead – Acid battery, Nicad etc. 3) Flow battery is the one in which all the constituents of the battery fow thought the battery. E.g. Hydrogen-Oxygen Fuel cell. Zinc-Carbon Battery : It consists of Zinc can which acts as anode. A graphite rod is placed in the middle of the can acts as cathode. A mixture of MnO 2 , NH 4 Cl and ZnCl 2 acts as electrolyte. A small amount of starch is added to the electrolytic mixture to keep it in the form of a paste so that chance of undergoing leakage is less. When it supplies voltage the following cell reactions take place. Zn Zn 2+ + 2 e - (oxidation) Anode : + - 2 + - Cathode: 2 MnO 2 + 2NH 4 + 2 Cl + Zn + 2 e Mn 2 O 3 + [Zn(NH 3 ) 2 ]Cl 2 + H 2 O (Reduction) + - Net reaction: Zn + 2 MnO 2 + 2 NH 4 + 2 Cl Mn 2 O 3 + [Zn(NH 3 ) 2 ]Cl 2 + H 2 O The voltage supplied by the cell is 1.5 V.
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In designing Zn-Carbon cells, corrosion and other undesirable reactions cause difculties. Luckily, the over potential for hydrogen evolution on zinc is quite high in mildly acidic or alkaline solutions. Another source of corrosion is direct reaction of oxygen in air ingress to the cell. In order to protect against this problem, the cell is sealed and access of air is restricted as far as possible. Uses : It is used in the areas where low voltages are required such as calculators, remotes, wall clocks, etc. Storage cell: it is the one which can act both as voltaic cell and electrolytic cell. When it functions as voltaic cell, it supplies electric current and the process is known as discharging. When it functions as electrolytic cell, it receives electric current and this process is known as charging. So it can be used for a large no. of cycles of charging and discharging. The best example for storage cell is lead acid battery or lead acid accumulator. Lead-acid battery: Lead-acid is the oldest rechargeable battery in existence.
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  • Fall '16
  • Volt, solar cells, Rechargeable battery, Electrochemical cell, Lithium-ion battery

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