When the computer decides the time is right, it disengages the clutch automatically, selects a different gear and then re-engages the clutch. Bigger gears produce extra velocity instead of torque, and that is great for clean  driving to the freeway.  Automatic gearboxes can sap more electricity with additional fluid couplings https://gearboxauto43073.blogunteer.com/33128096/little-known-facts-about-gearbox-auto