Skip to main content

Mechanical Board Exam Review Question: Thermodynamics Elements (ANSWERS)

Here are the answers to the questions posted yesterday on the topic THERMODYNAMICS. Please feel free to comment or ask for clarifications.
1. The state of a simple substance can be defined by at least how many properties (e.g. pressure, mass, temperature, density)?
ANSWER: B. TWO

2. The ability of a heat engine to convert the supplied heat to work is referred to as…
ANSWER: A. THERMAL EFFICIENCY

3. To increase the efficiency of a Carnot cycle…
ANSWER: C. BOTH a AND b
Increasing the max temperature and decreasing the min temperature will increase the area in the T-s diagram meaning more work for the same heat input.

4. The area under the curve of the process plotted in the p-V diagram corresponds to…
ANSWER: B. WORK NON-FLOW (INTEGRAL OF pdV)

5. The value of n, in the equation PVn=C when the process is isothermal?
ANSWER: A. 1

6. The value of n, in the equation PVn=C when the process is isometric?
ANSWER: C. INFINITY

7. In the T-s diagram, the area under the process curve corresponds to…
ANSWER: A. HEAT OF THE PROCESS (Q)

8. What law of thermodynamics introduced the concept of entropy?
ANSWER: B. SECOND LAW
The second law of thermodynamics explains irreversibility of the process and introduced the concept of entropy.

9. A device that converts heat energy to shaft work.
ANSWER: B. HEAT ENGINE

10. A thermodynamic process characterized by a straight vertical line in the T-s diagram.
ANSWER: B. ADIABATIC PROCESS
The horizontal axis of the T-s diagram is entropy, so straight vertical line is a constant entropy process (adiabatic or reversible isentropic).

Comments

  1. im preparing for board examination
    Put some
    situational
    question on

    BOILER'S/safety and maintenance

    ReplyDelete

Post a Comment

Popular posts from this blog

BOARD EXAM TIP: Which Review Center?

First of all, I would like to apologize for a long time I haven't posted anything but introduction. The reason for that is I'm busy optimizing the design of this site. I'm hoping that the make over is good. Anyway, I would like to dedicate this article to those who are going to take/retake the board exam this coming October. My sincere wish that you bring out the best among yourselves and may the deserving ones pass the exam.




Going back to the One-Million-Peso worth question: "Which review center should I enroll?", I would like to answer that in the most unbiased way I can. Of course, I'm only human and I had also my preferences but I will try my best to hide it.

To start with I will enumerate some of the prominent review centers that offer board exam reviews for mechanical engineering in the Philippines.

1. Alcorcon (Cebu & Manila)
2. Excel (Cebu & Manila)
3. Linx Engineering (Manila)
4. MERIT (Manila)
5. PRIME (Cebu)
6. RLB's CDTC (Manila)
I'…

PAST MECHANICAL BOARD EXAM QUESTION: Machine Design Set-1 (solutions and answers)

The following are the solutions and answers to MODIFIED PAST MECHANICAL BOARD EXAM QUESTION: Machine Design Set-1 posted on this blog last Saturday, November 14, 2009.




Again, I want to stress out that most of the questions here are modified from its original form for the purpose of improving the question.

Past Mechanical Engineering Board Exam Question Number 1
A 4 inches diameter short shaft carrying 2 pulleys close to the bearings transmits how much horsepower if the shaft makes 120 rpm.

A.200HP               B. 199 HP

C.198 HP              D. 202 HP

P = (D3N )/38 -- for mula for short shafts from PSME code

P = (4)3(120)/38

P= 202 HP

Past Mechanical Engineering Board Exam Question Number 2
An instrument that measures the hardness of the work piece in terms of elasticity.

a. Durometer

b. Scleroscope

c. Mohs's Scale

d. Brinell Tester

Source: Machinery’s Handbook

SOLUTION TO MECHANICAL BOARD EXAM PROBLEMS: Power Set-1

Here are the solutions to board problems given at Power Subject Set-1. If you do not understand anything, feel free to write a comment voicing out your concern. I'm still looking for better ways to present my solution. I still don't know how to present equations and mathematical symbols with blogger. Please bear with me.

1. An automobile tire is inflated to 32psig pressure at 50 degree F. After being driven, the temperature rises to 75 degree F. Determine the final gage pressure assuming the volume remains constant. (Electrical Engineering Board Exam Problem)

Solution:
Since volume is constant, use Charles’ Law on constant volume processes.
P1/T1=P2/T2
Note: P and T should be absolute.

(32+14.7)/ (50+460) =P2/ (75+460)

P2=48.99 psia

Converting back to gage pressure,

P2g=48.99-14.7

P2g=34.29 psig


2. Four hundred cubic centimeters of gas at a pressure of 740 mmHg absolute and temperature of 18 degree C undergoes a process until the pressure and temperature becomes 760 mmHg abso…