Convection is the mode of heat transfer which involves bulk motion of a fluid to transfer heat. Energy transfer by convection is primarily restricted to fluids. Fluids can be both liquids and gases.
A UPS (Uninterruptible Power Supply) is a device that provides battery backup when the electrical power fails or drops to an unacceptable voltage level.
Small UPS systems provide power for a few minutes; enough to power down the computer in an orderly manner, while larger systems have enough battery for several hours.