# Difference Between Lower Pair And Higher Pair

## What Is Lone Pair?

When two elements of a pair are joined together with the surface contact between them, the joint is referred to as lower pair. Area of two elements comes together when relative motion occurs between the elements to form a lower pair e.g nut and screw, universal joint used to connect two propeller shafts.

### What You Need To Know About Lower Pair

• When the two elements of a pair have surface (area) contact while in motion the pair is referred to as a lower pair.
• Area of two elements comes together when relative motion occurs between the elements to form a lower pair.
• These are kinematic pairs having sliding joints which are in surface to surface contact.
• All sliding pairs, turning pairs and screw pairs form lower pair. For example a nut turning on a screw, a shaft rotating in a bearing, an universal joint all pairs of a slider crank mechanism, a pantograph etc.

## What Is Higher Pair?

Generally, a higher pair is a constraint that requires a line or point contact between the elemental surfaces. For example, the contact between a cam and its follower is a higher pair referred to as cam joint. In the higher pair, only one point or line are responsible to form a joint between two links. The elements of higher pair must have a curve in its shape. These joints are found in the cylinders or spheres of equal or different radius which have their axis parallel to each other. A cylinder or sphere lying on a flat surface has a point contact and makes a higher pair.

### What You Need To Know About Higher Pair

• When the two elements have point or line contact while in motion then the pair is referred to as higher pair.
• In the higher pair only one point or line is responsible to form a joint between two links.
• The elements of higher pair must have curve in its shape.
• These joints are found in the cylinders or spheres of equal or different radius which have their axis parallel to each other.
• Belt, rope and chain drives, gears, the cam and follower ball and roller bearings, a wheel rolling on a surface etc, all form higher pairs.