V

Viscosity

η = (F/A)/(dv/dx); SI unit: Pa·s (Poise)
Quick Reference
Formula / Notationη = (F/A)/(dv/dx); SI unit: Pa·s (Poise)
Also Known AsDynamic viscosity, absolute viscosity, fluid viscosity, η (eta)

What is Viscosity?

The resistance of a fluid to flow, arising from intermolecular forces and internal friction. High viscosity fluids flow slowly (honey, motor oil). Viscosity decreases with increasing temperature for liquids. Expressed in Pascal-seconds (Pa·s) or centipoise (cP).

Formula & Notation

η = (F/A)/(dv/dx); SI unit: Pa·s (Poise)

Other Names / Synonyms: Dynamic viscosity, absolute viscosity, fluid viscosity, η (eta)

Properties & Characteristics

Viscosity is the resistance of a fluid to flow, arising from internal friction between fluid layers moving at different velocities. Dynamic viscosity (η) is measured in Pa·s (pascal-seconds) or millipoise. Kinematic viscosity is dynamic viscosity divided by density. Viscosity generally decreases with increasing temperature for liquids and increases with temperature for gases.

Uses & Applications

Viscosity is a critical property in the design of pumps, pipes, and lubrication systems. The viscosity of motor oils and lubricants determines their performance at different temperatures. In pharmaceutical manufacturing, viscosity affects drug formulation and delivery.

Safety Information

Highly viscous chemicals are harder to pump and mix, potentially causing process hazards. Low-viscosity volatile liquids can spread and evaporate rapidly, increasing fire and inhalation risks. Safe handling procedures account for the viscosity of chemical substances.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Viscosity
Formula η = (F/A)/(dv/dx); SI unit: Pa·s (Poise)
Synonyms Dynamic viscosity, absolute viscosity, fluid viscosity, η (eta)

Frequently Asked Questions

The resistance of a fluid to flow, arising from intermolecular forces and internal friction. High viscosity fluids flow slowly (honey, motor oil). Viscosity decreases with increasing temperature for liquids. Expressed in Pascal-seconds (Pa·s) or centipoise (cP).

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