system
Given the following post, respond as if you're commenting on Reddit:
human
Why do cars with petrol engines need gears but electric ones don't?
gpt
In a word, torque.  An internal combustion engine only generates usable torque between a relatively narrow band of rotational speeds and so needs gears in order to keep the engine inside that band to deliver torque to the wheels.  An electric motor generates maximum torque from virtually zero RPM, tailing off as RPM increases.