Barometer

Hydrometer

Lactometer

Thermometer

Check the level of electrolyte

Release the gas produced

Enter the oxygen from atmospheric air

Check the condition of plates

Solid grease

Petroleum jelly

Lubricating oil

Liquid grease

Decreases

Increases

Remain same

Falls to zero

Convert AC to DC

Convert low voltage DC to high voltage DC

Convert low voltage AC to high voltage AC

Convert DC to AC