# Viscosity Coefficient

Viscosity coefficient, abbreviated as \(\eta\) (Greek symbol eta), also called coefficient of viscosity or absolute viscosity, is the tangential friction force required to preserve a unit velocity gradient between two parallel layers of liquid of unit area. The greater the coefficient of viscosity the greater the force required to move the layers at a velocity.

## Viscosity Coefficient formula |
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\(\large{ \eta = \frac { F_t \; l } { A \; v } }\) | ||

Symbol |
English |
Metric |

\(\large{ \eta }\) (Greek symbol eta) = viscosity coefficient | \(\large{\frac{lbf - sec}{ft^2}}\) | \(\large{Pa - s}\) |

\(\large{ A }\) = area | \(\large{in^2}\) | \(\large{mm^2}\) |

\(\large{ l }\) = distance between the layers | \(\large{in}\) | \(\large{mm}\) |

\(\large{ F_t }\) = tangential force | \(\large{lbf}\) | \(\large{N}\) |

\(\large{ v }\) = velocity | \(\large{\frac{ft}{sec}}\) | \(\large{\frac{m}{s}}\) |