The operation of an automatic transmission is explained here with help of animation. Allison-1000 transmission model, which has 6 speed and reverse is used for this purpose.
source/image(PrtSc): Learn Engineering
The video starts with an explanation of planetary gear set. Just by engaging few clutch packs different output speed can be achieved in automatic transmission. A brief introduction of the torque converter is also given here.Watch the video from Learn Engineering for more info:
An automatic transmission and a manual transmission accomplish exactly the same thing, but they do it in totally different ways.On an automatic transmission, brilliant engineering determines which gear is engaged without you having to do a dang thing except to press the gas or the brake pedals. It’s automotive magic.
Like other transmission systems on vehicles, it allows an internal combustion engine, best suited to run at a relatively high rotational speed, to provide a range of speed and torque outputs necessary for vehicular travel. The number of forward gear ratios is often expressed for manual transmissions as well (e.g., 6-speed manual).