Use of Gears-

●      To reverse the direction of rotation

●      To increase or decrease the speed of rotation

●      To move rotational motion to a different axis

●      To keep the rotation of two axis synchronized

Advantages of Teeth-

●      They prevent slippage between the gears – therefore axles connected by gears are always synchronized exactly with one another.

●      They make it possible to determine exact gear ratios – you just count the number of teeth in the two gears and divide. So if one gear has 60 teeth and another has 20, the gear ratio when these two gears are connected together is 3:1.

●      They make it so that slight imperfections in the actual diameter and circumference of two gears don’t matter. The gear ratio is controlled by the number of teeth even if the diameters are a bit off.