1% to 2%

2% to 5%

5% to 12%

12% to 20%%

cooling and lubrication

insulation and lubrication

insulation and cooling

insulation, cooling and lubrication

To work as a control transformer

To work as a variable transformer

To work as a distribution transformer

To work as an isolating transformer

increase output power

increase output voltage

increase output current

none of these

an air-tight metallic drum fixed at the top of the oil-tank

an air-tight metallic drum fixed at the bottom of the oil-tank

overload protection device

none of these