Question

Fingers are wetted at intervals when currency notes are being counted. Why?

Answer 1

When the hand is moist, adhesive force (attraction between dissimilar molecules) exists between the water molecules and the hand, as well as between the water molecules and the paper. The cohesive force (surface tension) is what keeps water molecules together and adds to the ease with which paper may be turned. The adhesion is weaker when the hand is used alone.

Complete step by step answer:
There are two types of forces which are associated with bulk properties, they are adhesive force and cohesive force. Adhesive forces act between dissimilar molecules and cohesive forces act between similar molecules. Adhesion is the force of attraction that exists between water molecules and other types of molecules.
While counting the notes might stick to one another, when the fingers are wet the adhesive force between the note and water helps it to stick to the hand and helps to count faster.

Note:
The consequences of adhesion include capillary action and the formation of a meniscus (the curved surface created by any liquid in a cylinder). Adhesion is generated by electrostatic or mechanical forces that exist between two distinct types of material. The liquid spreads all over the surface due to a strong adhesive force. Water molecules have a lot of cohesion force. The consequences of cohesion include surface tension, meniscus, and capillary action. Hydrogen bonding and Van der Waals forces are responsible for cohesion. Water droplets develop on any surface due to a strong cohesive force.