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Viscosity of a fluid is a measure of a fluid’s resistance to motion created by. pressure. driving forces. shear stress.

Newtonian fluids are defined by their relationship between the shear stress and shear strain rates, which exhibits. linear characteristics. nonlinear characteristics. combined linear and nonlinear characteristics.

Reynolds number is related to the characteristics of. a stationary state of the fluid. a moving state of the fluid. any state of the fluid.

Reynolds number is proportional to. the traveling distance. the velocity. the pressure of a fluid.

Control volume in a fluid dynamic analysis means. a conveniently selected volume of the fluid for the analysis. the volume of the fluid in which the Reynolds number is constant. the volume of the fluid in which the fluid properties are constant.

A laminar fluid flow means a. low velocity. high velocity. quasi‑stagnant fluid flow.

Laminar flow of compressible fluids normally takes place with Reynolds number in the range of. 0 to 10. 10 to 100. 100 to 1000.

In general, fluid flows in microsystems are. laminar. turbulent. neither laminar nor turbulent.

The continuity equation is used to evaluate. volumetric flow rate. relationship between the motion and the driving forces. the induced forces in a moving fluid.

The momentum equation is used to evaluate. volumetric flow rate. relationship between the motion and the driving forces. the induced forces in a moving fluid.

We will use. continuity equation to assess the fluid induced forces on microsystem components. momentum equation to assess the fluid induced forces on microsystem components. equation of motion to assess the fluid induced forces on microsystem components.

Hydraulic diameter is used to evaluate the cross‑sectional area of fluid flowing in. circular conduits. rectangular conduits. any shape of conduits.

CFD stands for. critical fluid dynamics. computational fluid dynamics. computerized fluid dynamics.

Navier–Stokes equations relate. pressure–velocity. pressure–density change. pressure–viscosity in a moving fluid.

Surface tension in a fluid is a form of. applied tension at the surface of the fluid. an existing tension at the fluid surface. tension that makes the surface of the fluid.

Surface tension is the principal cause for. capillary. newtonian. laminar flow of a fluid.

The coefficient of surface tension of a fluid is a measure of the magnitude of the. inherent strength. surface tension. topology of a fluid surface.

The capillary height of a fluid in a small tube is. equal to the diameter of the tube. directly proportional to the diameter of the tube. inversely proportional to the diameter of the tube.

Pressure drop at two points in a fluid drives the flow of the fluid in a circular conduit. It is inversely proportional to the. second power of the diameter of the conduit. third power of the diameter of the conduit. fourth power of the diameter of the conduit.

The driving force in the piezoelectric pumping of fluids in minute conduits is of the. linear nature. surface nature. volumetric nature.

A rarefied gas means the gas is at. extremely low pressure. intermediate pressure. vacuum.

A good estimate of the MFP for gases is. 65 nm. 75 nm. 130 nm.

A good estimate of the MFP for liquids is. 65 nm. 75 nm. 130 nm.

The Knudsen number is defined as. the density of the gas over the physical size of the confinement. the mean free path over the physical size of the confinement. the velocity of the gas over the speed of sound.

Conventional fluid dynamics theories are valid for. very small Knudsen numbers. large Knudsen numbers. very large Knudsen numbers.

The Mach number is defined as. the density of the gas over the physical size of the confinement. the mean free path over the physical size of the confinement. the velocity of the gas over the speed of sound.

A gas is considered to be compressible if the Mach number is. less than than 0.3. equal to than 0.3. greater than 0.3.

The larger the Knudsen number, the confinement of the gas becomes. smaller. larger. remains the same.

A rule of thumb to classify a rarefied gas is. Kn<0.1, Ma<0.3. Kn>0.1, Ma<0.3. Kn>0.1, Ma>0.3.

The Navier‑Stokes equations can be reasonably used for gas flow with a Knudsen number that is less than. 0.01. 0.1. 1.0.

One could use the Navier‑Stokes equation for gas flow between the values of 0.01 and 0.1 by using. any boundary condition. nonslip boundary condition. slip boundary condition.

Thermal conductivity of a material is a measure of its. conductance to heat. resistance to conducting heat and electricity. speed of heat conduction.

Metals are. better than semiconductors and ceramics in conducting heat. worse than semiconductors and ceramics in conducting heat. about the same as semiconductors and ceramics in conducting heat.

Thermal diffusivity of a material is a measure of its. conductance to heat. resistance to conducting heat and electricity. speed of heat conduction.

Heat flux is a measure of heat conduction in a solid per unit. length for a given period of time. area for a given period of time. volume for a given period of time.

Heat flux is a. scalar quantity. vector quantity. tensor quantity.

Heat generation in a solid by electric resistance is related to. current and resistance. voltage and resistance. inductance and resistance.

For micro thermal actuators, one would choose the actuating materials with. high thermal conductivity. high thermal diffusivity. neither of the above.

Newton’s cooling law is used for microsystem components in contact with. fluids. another solid component. any substance.

The heat transfer coefficient of a fluid in contact with a solid is. equal to the velocity of the fluid flow. directly proportional to the velocity of the fluid flow. inversely proportional to the velocity of the fluid flow.

The natural convective heat transfer is prompted by. the driving forces of the fluid due to heating of the fluid. the pressure drop in the fluid due to heating of the fluid. the change of density of the fluid due to heating of the fluid.

The surface of the solid becomes virtually impermeable to heat if the surrounding fluid is moving at. high velocity. low velocity. stagnant velocity.

The larger the Nusselt number, the. larger the heat transfer coefficient in the fluid. smaller the heat transfer coefficient in the fluid. same the heat transfer coefficient in the fluid.

In thermally‑actuated micropumps, one needs to pay attention to the. conductive heat transfer between the actuating elements and the contacting fluid. convective heat transfer between the actuating elements and the contacting fluid. radiative heat transfer between the actuating elements and the contacting fluid.

When a thermally‑actuated element is in contact with a working fluid, the interface temperature is normally. lower than the bulk fluid temperature. about the same as the bulk fluid temperature. higher than the bulk fluid temperature.

There are generally. 3 types of boundary conditions involved in heat conduction analysis of solids. 4 types of boundary conditions involved in heat conduction analysis of solids. 5 types of boundary conditions involved in heat conduction analysis of solids.

When designing a thermally‑actuated beam element, one will be primarily concerned with. the weight of the beam. the mechanical strength of the beam. the thermal response of the beam.

Heat conduction analysis is necessary for the subsequent. thermal stress in the design of a thermally‑actuated micro device. heat dissipation in the design of a thermally‑actuated micro device. safety analysis in the design of a thermally‑actuated micro device.

Heat transportation in solids in macroscale is by. vibration of the lattices of molecules. the movement of phonons and photons in molecules. the movement of electrons in molecules.

Heat transportation in solids in submicrometer and nanoscales is dominated by. the vibration of the lattices of molecules. the movement of phonons and photons in molecules. the movement of electrons in molecules.

MFP stands for. molecular free path for energy carriers in a substance. minimum free path for energy carriers in a substance. mean free path for energy carriers in a substance.

MFT stands for. molecular free time for energy carriers in a substance. minimum free time for energy carriers in a substance. mean free time for energy carriers in a substance.

One needs to be concerned with the validity of using continuum heat transfer theories when the size of the solids is. greater than 1 μm. about equal to 1 μm. less than 1 μm.

The thermal conductivity of solids of submicrometer and nanoscale is. less than the value of the same material at macro scale. about equal to the value of the same material at macro scale. greater than the value of the same material at macro scale.

The additional term in the heat conduction equation for solids of submicrometer and nanoscales is related to. the extra time in heat transmission. the extra velocity in heat transmission. the extra heat in heat transmission.