Assertion (A): Helical gears are used for transmitting motion and power between intersecting shafts, where as straight bevel gears are used for transmitting motion and power between two shafts intersecting each other at 900.
Reason (R): In helical gears teeth are inclines to the axis of the shaft and are in the form of a helix, whereas in bevel gears, teeth are tapered both in thickness and height from one end to the other.