Automobile Engineering in ME
A battery can be charged by

Applying a voltage in the same direction to that of charging
Applying voltage in the reverse direction to that of charging
Adding sulphuric acid
Adding distilled water

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Automobile Engineering in ME
The function of a second ring is that it is a

Cushion ring which prevents piston slap and knock
Back up oil control ring which will work in place of the bottom ring when it is broken
Back up compression ring which will work in place of the top ring when it is broken
Compression ring and aids the top ring in sealing and cooling

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