Biot number signifies the ratio of

convective resistance in the fluid to conductive resistance in the solid
conductive resistance in the solid to convective resistance in the fluid
inertia force to viscous force in the fluid
buoyancy force to viscous force in the fluid

Correct answer: convective resistance in the fluid to conductive resistance in the solid

Solution

The Biot number is defined as the ratio of internal conductive resistance to external convective resistance. In many exam options, this is described equivalently as convective resistance in the fluid to conductive resistance in the solid, depending on wording.

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