Page 78 - Electrician - TT (Volume 1)
P. 78

ELECTRICIAN - CITS


































           •  It is observed that no water is formed in the reaction.  So that  the specific gravity remain unchanged during
              charging and discharging.
           •  So that the cell is not damaged if kept long time in a fully discharged state
           Characteristics

           •  Emf fully charged state -----   1.4 V
           •  Reaches to 1.2 V on discharge

           •  Emf fully discharged state -----   1.15 V
           •  Mechanical strength is good since they are made of steel.
           •  The cell can withstand heavy charge and discharge currents.

           •  Internal resistance is large and efficiency is lower than lead acid battery.
           •  With increase in temperature of the cell the capacity increases.
           Comparison between charge & discharge states

           During discharge
           •  The negative plate turns in to ferrous hydroxide

           •  The positive plate turns in to lower hydroxide of nickel
           •  The specific gravity of electrolyte remains constant
           •  The per cell voltage falls from 1.4 V to 1.15

           During charging
           •  The negative plate turns in to iron
           •  The positive plate turns in to l nickel hydroxide

           •  The specific gravity of electrolyte remains constant
           •  The per cell voltage increases from 1.15 to 1.4 V








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 CITS : Power - Electrician & Wireman - Lesson 13-19  CITS : Power - Electrician & Wireman - Lesson 13-19
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