Question

To which type of liquid is Bernoulli’s theorem applicable.

Answer 1

Bernoulli’s theorem is observed in liquids flowing through pipes or cylindrical objects. The uniformity and regularity of its motions are its characteristic properties. Thus the type of liquids that support its properties follow the theorem.

Complete answer:
Bernoulli’s theorem is associated with the motion of liquids known as fluid dynamics.
The phenomenon of a fluid speeding up (enhancing its velocity) in constricted areas so as to exert minimum pressure in areas with small cross sectional diameter is explained by Bernoulli's theorem. It suggests that the motion of the liquid should be horizontal in order to avoid gradient in gravitational potential energy which is responsible for the decrease in fluid pressure associated with enhanced fluid velocities.
This theorem is based on the law of conservation of energy and it is applicable to only ideal fluids having a steady and streamlined flow. Thus Bernoulli's theorem is followed by only those fluids that are incompressible have a streamlined flow and no viscosity.

Additional Information:
The streamlined flow is an ideal flowing condition in which each particle moves along the same path having the same magnitude and direction of velocity as that of other particles in the fluid. The regularity of such a flow remains undisturbed by circular currents or Eddie currents.
Turbulent flow or non-streamlined flow is the exact opposite of streamlined flow which suffers circular currents or Eddie currents having a non-uniform velocity throughout the bulk of the fluid.

Note:
The absence of viscosity is needed to avoid laminar flow of fluids in which each layer pulls back another layer just below it. The layers in contact with the pipe walls experience maximum drag and this results in a velocity gradient.