<P> In the battery used for electric vehicles, Nominal battery performance is usually specified for working temperatures somewhere in the + 20 ° C to + 30 ° C range; however, the actual performance can deviate substantially from this if the battery is operated at higher or, in particular, lower temperatures, so some electric cars have heating and cooling for their batteries . </P> <P> Heat sinks are widely used in electronics, and have become almost essential to modern central processing units . In common use, it is a metal object brought into contact with an electronic component's hot surface--though in most cases, a thin thermal interface material mediates between the two surfaces . Microprocessors and power handling semiconductors are examples of electronics that need a heat sink to reduce their temperature through increased thermal mass and heat dissipation (primarily by conduction and convection and to a lesser extent by radiation). Heat sinks have become almost essential to modern integrated circuits like microprocessors, DSPs, GPUs, and more . </P> <P> A heat sink usually consists of a metal structure with one or more flat surfaces to ensure good thermal contact with the components to be cooled, and an array of comb or fin like protrusions to increase the surface contact with the air, and thus the rate of heat dissipation . </P> <P> A heat sink is sometimes used in conjunction with a fan to increase the rate of airflow over the heat sink . This maintains a larger temperature gradient by replacing warmed air faster than convection would . This is known as a forced air system . </P>

For high efficiency of transfer of power internal resistance of source should be