Chapter 2 Multiple Choice Questions

* not completed

1) Match the correct formula to each of the following:

1a.

$\kappa =\frac{k}{\rho c}$

Stefan-Boltzmann law Diffusivity Enthalpy Carnot efficiency Fourier's law of heat conduction Exergy

* not completed

1b.

$P_{\text{e}}=\epsilon \sigma T^4$

Exergy Fourier's law of heat conduction Carnot efficiency Enthalpy Stefan-Boltzmann law Diffusivity

* not completed

1c.

$h=u+pv$

Exergy Carnot efficiency Fourier's law of heat conduction Stefan-Boltzmann law Diffusivity Enthalpy

* not completed

1d.

$\eta =1–\frac{T_{\text{lower}}}{T_{\text{upper}}}$

Diffusivity Stefan-Boltzmann law Enthalpy Fourier's law of heat conduction Carnot efficiency Exergy

* not completed

1e.

$\dot{Q}=kA(T_1-T_2)/d$

Exergy Carnot efficiency Fourier's law of heat conduction Enthalpy Stefan-Boltzmann law Diffusivity

* not completed

1f.

$X=Q\left(1-\frac{T_{\text{a}}}{T_1}\right)$

Exergy Enthalpy Stefan-Boltzmann law Diffusivity Fourier's law of heat conduction Carnot efficiency

* not completed

2) What is the missing text in the following statement?

'A system operating … cannot convert all the heat absorbed from a reservoir into the same amount of work.'

in an open cycle correct incorrect

in a closed cycle correct incorrect

between two reservoirs at different temperatures correct incorrect

on a real fluid correct incorrect

in isolation correct incorrect

* not completed

3) Which of the following statements are true?
Please select all that apply.

A good absorber of solar radiation when heated to 500 K is necessarily a good emitter of thermal radiation. correct incorrect

Isotherms can move in unsteady heat conduction but not in steady heat conduction. correct incorrect

The Nusselt number has no physical dimensions. correct incorrect

The Carnot efficiency tends to infinity as the temperature of the lower reservoir tends to absolute zero. correct incorrect

The first law of thermodynamics only applies to mechanical work. correct incorrect

The Prandtl number depends on the properties of the material. correct incorrect

Radiation is the only form of heat transfer in a vacuum. correct incorrect

* not completed

4) The heat required to change the phase of unit mass of material is called the ______ ______.

Your response

* not completed

5) The basic forms of heat transfer are conduction, __________, and radiation.

Your response

* not completed

6) The handle of an iron rod 50 cm long placed in a hot fire gets uncomfortably hot after 1 minute. What length of iron rod could be comfortably held by its handle for 5 minutes after the end of the rod was placed in the fire?

2.5 m correct incorrect

1.25 m correct incorrect

1.12 m correct incorrect

* not completed

7) Heat pipes take advantage of the ____ ____ of a liquid to give high heat transfers.

Your response

* not completed

8) The increase in solar energy received by the Earth if the temperature of the outer surface of the Sun, 5800 K, increased by 2% would be approximately:

0.5% correct incorrect

2 % correct incorrect

6% correct incorrect

8% correct incorrect

* not completed

9) A planet with no atmosphere, which has a radius a third that of Earth, is orbiting a star identical in emission to our Sun at a radius half that of the Earth's. If the albedo of the planet is 0.825, what temperature is its surface?

510 K correct incorrect

255 K correct incorrect

85 K correct incorrect

765 K correct incorrect

* not completed

10) Carbon dioxide levels in the atmosphere are expressed in units of parts per million by volume, ppmv. What is the approximate multiplying factor that would convert the amount of CO₂ to parts per million by mass?

~1.5 correct incorrect

~0.66 correct incorrect

~0.75 correct incorrect

~2 correct incorrect

* not completed

11) Global warming is approximately proportional to the _____ emissions of CO₂, Σ, because the declining atmospheric absorption with increasing Σ is offset by the decreasing uptake of _____ and CO₂ by the oceans.

Your response

* not completed

12) Which of the following statements are true?
Please select all that apply.

The heat transfer at constant pressure equals the increase in enthalpy ΔH. correct incorrect

The amount of heat given out in the combustion of carbon is given by the increase in ΔH in the reaction C + O₂ -> CO2. correct incorrect

The work done by the adiabatic expansion of a fluid in a turbine equals the increase in enthalpy ΔH. correct incorrect

The enthalpy of a fluid remains unchanged when passing through an expansion valve. correct incorrect

* not completed

13) Under conditions of constant pressure and temperature, a reaction will occur spontaneously when the change in the _____ function is _______.

Your response

* not completed

14) Which of the following statements are true?
Please select all that apply.

Isothermal systems operate at constant temperature. correct incorrect

Adiabatic systems are always in equilibrium with their surroundings. correct incorrect

The combustion of carbon is an endothermic reaction. correct incorrect

The main contribution to the heat of combustion comes about from the relatively weak double bond in oxygen. correct incorrect

Entropy is unchanged in an irreversible process. correct incorrect

The decrease in Gibbs free energy in a chemical reaction equals the maximum amount of work that can be obtained from the reaction. correct incorrect

In an electrical resistance heater, the input exergy equals the electrical energy dissipated in the heater. correct incorrect

* not completed

15) Estimate the work done by a compressor in raising the pressure of 100 kg of water from 1 to 200 atmospheres.

2 MJ correct incorrect

200 kJ correct incorrect

2 kJ correct incorrect

* not completed

16) The height of the potential barrier that two interacting molecules have to overcome is called the __________ _______.

Your response

* not completed

17) A catalyst speeds up a reaction by…

increasing the energy released in the reaction. correct incorrect

by providing a route with a lower activation energy. correct incorrect

being consumed in the reaction. correct incorrect

* not completed

18) For steady flow of a perfect fluid through a constriction in a horizontal tube, which of the following statements are true?
Please select all that apply.

The mass flow rate is the same inside and outside the constriction. correct incorrect

The pressure is higher inside the constriction. correct incorrect

The fluid slows down as it passes through the constriction. correct incorrect

The total energy of the fluid is the same inside and outside the constriction. correct incorrect

* not completed

19) Match the formula to each of the following:

19a.

$\mathit{∆}U=Q+W$

Mass conservation Internal energy Input work in an adiabatic compression, when changes in kinetic and potential energy can be neglected Bernoulli’s equation

* not completed

19b.

$\frac{p}{\rho }+gz+\frac{1}{2}{u}^2=\text{const.}$

Input work in an adiabatic compression, when changes in kinetic and potential energy can be neglected Mass conservation Internal energy Bernoulli’s equation

* not completed

19c.

$\rho uA=\text{const.}$

Mass conservation Input work in an adiabatic compression, when changes in kinetic and potential energy can be neglected Bernoulli’s equation
Internal energy

* not completed

19d.

$W=h_2 – h_1$

Mass conservation Bernoulli’s equation
Input work in an adiabatic compression, when changes in kinetic and potential energy can be neglected Internal energy

* not completed

20) A fluid of density ρ and coefficient of dynamic viscosity μ moves with velocity U in between two parallel surfaces separated by a gap d. The viscous shear force per unit area on each surface is given by…

μρ/Ud. correct incorrect

ρUd/μ. correct incorrect

μρ/d. correct incorrect

μρU/d. correct incorrect

μU/d. correct incorrect

* not completed

21) The fundamental units of kinematic viscosity are given by…

L²T^-1. correct incorrect

ML T^-1. correct incorrect

L^-1T². correct incorrect

ML²T^-2. correct incorrect

L T^-1. correct incorrect

* not completed

22) The typical order of magnitude of the Reynolds' No. for a fluid to switch from laminar flow to turbulent flow is…

1. correct incorrect

10³. correct incorrect

10². correct incorrect

10⁶. correct incorrect

10^-3. correct incorrect

* not completed

23) The flow of water over a small model wing and the flow of air over a full-scale wing have the same Reynolds' No. Is it true that the flow regime is the same in both cases?

Yes correct incorrect

No correct incorrect

* not completed

24) The lift force on an aerofoil with a lift coefficient $C_{\mathrm{L}}$ in a fluid with density ρ moving with velocity U is given by…

$\frac{1}{2}{C}_{\mathrm{L}} \rho UA$. correct incorrect

$\frac{1}{2}{C}_{\mathrm{L}} \rho U{A}^2$. correct incorrect

$\frac{1}{2}\rho U{A}^2/C_{\mathrm{L}}$. correct incorrect

$\frac{1}{2}{C}_{\mathrm{L}} \rho U^{2}A$. correct incorrect