Gears and chain transmission

How to transfer rotational energy from one wheel to another? This simulation illustrates two possibilities:

1. Gears
2. Chain transmission

Gears are a mechanical system made of two discs with teeth that mesh smoothly into one another. The two gears are in contact at all times as a tooth of the driver gear pushes a tooth of the driven gear. The driver gear transfers its rotational movements to the driven gear, but the gears turn in opposite directions.

A chain transmission connects two gears that are not in contact.  Unlike a belt, a chain is made of links allowing a smooth transmission without sliding. The gears turn in the same direction.

In both cases, the speed of rotation of the driven gear depends on the dimensions of both gears.