The GATE Grind

GATE 2025 MT – Question 14

Transport Phenomena and Rate Processes · Fluid flow and momentum transfer · 1 mark · Multiple choice

At high temperatures, which empirical expression correctly describes the variation of dynamic viscosity $\mu$ of a Newtonian liquid with absolute temperature $T$? Given: $A$ and $B$ are positive constants.

  1. $\mu=A+BT$
  2. $\mu=A\exp(-B/T)$
  3. $\mu=A\exp(BT)$
  4. $\mu=A\exp(B/T)$

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (D) $\mu=A\exp(B/T)$

Explanation

Liquid viscosity decreases as thermal activation allows molecules to rearrange more easily. The empirical Arrhenius form μ=A exp(B/T), with A,B positive, has dμ/dT=−AB exp(B/T)/T²<0. Thus **D** has the appropriate dependence.