- Viscosity refers to the resistance to the flow of liquid arising as a result of the internal friction within the layers as they pass over other layer.
- Viscosity arises due to the strong intermolecular forces between the molecules that holds them together and resist the passing of layers over other.
- The layers of molecules of the flowing liquid that are in contact with the surface are stationary.
- Increase in the distance between the two layers increases the velocity of the upper layer.
- Flow of liquid with regular gradation of velocity while passing over other layer is termed as laminar flow.
- It is equal to the force when the velocity gradient and area of contact is unity. Therefore, η can be called the measure of viscosity.
- It is measured in unit called Nsm-2.
A liquid is streaming between two layers. Figure the shearing power if the shear speed is 0.25 m/s and has length 2 m and element thickness is 2Ns/m2.
d u = 0.25 m/s,
d z = 0.125/s
η = 2 Ns/m^2
F = η A du/dz
F = 2 Ns/m2 × 0.125 /s
F = 0.5 N/m2