Electrical Engineering ⇒ Topic : Chemical Changes During Recharging
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Sachin
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Chemical Changes During Recharging Consider a discharged lead-acid cell having both the plates converted to lead sulphate (PbS04).In order to recharge the cell, direct current is passed through the cell in the reverse direction to that in which the cell provided current. To do so, the anode is connected to the positive terminal of d.c. source and cathode to the negative terminal of the source as shown in Fig.(a). The electrolyte (H2S04) breaks up into hydrogen ions (H+H+) and sulphate ions (SO4). Hydrogen ions move towards towards cathode and sulphate ions move towards anode causing the following chemical reactions At anode. On reaching the anode, a sulphate ion (SO4- -) gives up its two extra electrons to become sulphate radical. These electrons given up at the anode move through the external circuit to the cathode where they are available to neutralise the positive ions (H+H+) arriving there. Since sulphate radical cannot exist, it enters into chemical reaction with water as under
figure (a)
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