What is the difference between Moment and Couple? • Moment of force is the measure of turning effect of a force about a point. A couple consists of two equal and opposite forces acting with two different but parallel lines of action. Each force has its own moment. • Moment of a force is dependent on the distance from the pivot and the magnitude of the force while the moment of a couple is the net effect of the two moments of the forces. Moment of a couple is independent of the location of the point considered. It is constant throughout the plane. The resultant moment of a couple is called a torque. • Torque, also called moment or moment of force, is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist. Couple - Two equal but opposite forces Torque - Moment of a couple 1. What is the importance of the Thermodynamics in the field of Mechanical Engineering? All the mechanical engineering systems are studied with the help of thermodynamics. Hence it is very important for the mechanical engineers. 2. How many Laws of Thermodynamics are there? There are three laws of the thermodynamics. First Law: Energy can be neither created nor destroyed. It can only change forms.In any process in an isolated system, the total energy remains the same. Second Law: When two isolated systems in separate but nearby regions of space, each in thermodynamic equilibrium in itself, but not in equilibrium with each other at first, are at some time allowed to interact, breaking the isolation that separates the two systems, and they exchange matter or energy, they will eventually reach a mutual thermodynamic equilibrium. The sum of the entropies of the initial, isolated systems is less than or equal to the entropy of the final exchanging systems. In the process of reaching a new thermodynamic equilibrium, entropy has increased, or at least has not decreased. Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum. 3. State Laws of conservation of energy? According to the laws of conservation of energy, “energy can neither be created nor be destroyed. It can only be transformed from one form to another.” 4. Is the boiler a closed system? Yes definitely the boiler is a closed system. 5. What is Carnot engine? It was being designed by Carnot and let me tell you that Carnot engine is an imaginary engine which follows the Carnot cycle and provides 100% efficiency. 6. Which formula forms a link between the Thermodynamics and Electro chemistry? Gibbs Helmholtz formula is the formula which forms the link between the thermodynamics and electromagnetism. ∆Hs/R = [∂ lnp /∂ (1/T)]x where: x – mole fraction of CO2 in the liquid phase p – CO2 partial pressure (kPa) T – temperature (K) R – universal gas constant α – mole ratio in the liquid phase (mole CO2 per mole of amine) 7. Which is the hardest compound known? Diamond. 8. What is Hess Law? According to the Hess law the energy transfer is simply independent of the path being followed. If the reactant and the product of the whole process are the same then same amount of energy will be dissipated or absorbed. 9. Which has more efficiency: Diesel engine or Petrol engines? Off course Diesel engine has the better efficiency out of two. 1. What is the difference between Critical Speed and Whirling Speed? Ans. In Solid mechanics, in the field of rotor dynamics, the critical speed is the theoretical angular velocity which excites the natural frequency of a rotating object, such as a shaft, propeller or gear. As the speed of rotation approaches the objects natural frequency, the object begins to resonate which dramatically increases system vibration. The resulting resonance occurs regardless of orientation.Whirling Speed is due to the unbalanced forces acting on a rotating shaft. 2. How a Diesel Engine Works as Generator? Ans. Diesel engine is a prime mover, for a generator, pump,and for vehicles etc. generator is connected to engine by shaft. mostly in thermal power plat ,there is an engine is used to drive generator to generate power. 3. Explain Second Law of Thermodynamics? Ans. The entropy of the universe increases over time and moves towards a maximum value. 4. Compare Brayton Cycle and Otto Cycle? Ans. The heat addition and rejection processes in Otto cycle are of constant volume, whereas in Brayton cycle, they are of constant pressure. -Otto cycle is the ideal cycle for spark ignition engines. -Brayton cycle is the ideal cycle for gas power turbines. 5. What is the purpose of Scrapper Ring? Ans. scrap the excess lube oil from the cylinder walls. there by preventing oil from entering combustion zone. 6. What is DTSI Technology? Ans. DTSI stands for Digital Twin Spark Plug Ignition. The vehicles with DTSI Technology use 2 spark plugs which are controlled by digital circuit. It results in efficient combustion of air fuel mixture. • Digital - Since the spark generation will be initiated by a microchip. • Twin - Since two spark plugs will be used. • Spark ignition - Since the ignition will be done via a spark. 7. How to Find, Ductile-Brittle Transition Temperature in Metals? Ans. The point at which the fracture energy passes below a pre-determined point for a standard Impact tests. DBTT is important since, once a material is cooled below the DBTT, it has a much greater tendency to shatter on impact instead of bending or deforming. 8. What is the importance of Thermodynamics? Ans. All the mechanical engineering systems are studied with the help of thermodynamics. Hence it is very important for the mechanical engineers. 9. What is the difference between P11 and P12 Pipes? Ans. P11 the chromium molybdenum composition that is 1% ofchromium and 1/4% of molybdenum P12 the chromium molybdenum composition that is 1% ofchromium and 2% of molybdenum 10. State difference between AntiFriction Bearing and Journal Bearing? Ans. Generally, journal bearings have higher friction force, consume higher energy and release more heat, but they have larger contact surface, so normally used in low speed high load applications. In anti friction bearings friction is less. One object just rolls over each other. 1. What is the difference between Technology and Engineering? Ans. Engineering is application of science. Technology shows various methods of Engineering. A bridge can be made by using beams to bear the load,by an arc or by hanging in a cable; all shows different technology but comes under civil engineering and science applied is laws of force/load distribution. 2. How to Measure Temperature in Wet Bulb Thermometer? Ans. Wet bulb temperature is measured in a wet bulb thermometer by covering the bulb with a wick and wetting it with water. It corresponds to the dew point temperature and relative humidity. 3. What are the Advantages and Disadvantages of using LPG in Car? Ans. Advantages 1. Complete combustion 2. Fuel saving 3. Homogenous combustion Disadvantages 1. As complete combustion is occurring ,more heat liberated,not advised for long journey, engine will be over heated 2. Installation is difficult 3. Reduce engine life efficiency 4. What is the difference between Speed and Economic Speed? Ans. The rated speed tells us about the maximum speed which can be achieved by a vehicle or some other machine but the economical speed means the speed limit at which the machine works efficiently with least consumption of fuel.eg-in normal bikes(not racing),the max.speed limit shown on speedometer is upto 120 kmph but companies always advice their customers to drive such bikes at around 60 kmph to have maximum mileage. 5. What is Powder Technology? Ans. Powder technology is one of the ways of making bearing material. In this method metals like bronze, Al, Fe are mixed and compressed to make an alloy. 6. State all the laws of Thermodynamics? Ans. There are three laws of the thermodynamics. First Law: Energy can be neither created nor destroyed. It can only change forms. In any process in an isolated system, the total energy remains the same. Second Law: When two isolated systems in separate but nearby regions of space, each in thermodynamic equilibrium in itself, but not in equilibrium with each other at first, are at some time allowed to interact, breaking the isolation that separates the two systems, and they exchange matter or energy, they will eventually reach a mutual thermodynamic equilibrium. The sum of the entropies of the initial, isolated systems is less than or equal to the entropy of the final exchanging systems. In the process of reaching a new thermodynamic equilibrium, entropy has increased, or at least has not decreased. Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum. 7. State the difference between Unilateral and Bilateral Tolerance? Ans. A unilateral tolerance is tolerance in which variation is permitted only in one direction from the specified direction.e.g. 1800 +0.000/-0.060 Bilateral tolerance is tolerance in which variation is permitted in both direction from the specified direction.e.g. 1800 +0.060/-0.060 8. What is the abbreviation of welding rod 7018? Ans. 7018 = 70=tensile strength 70000psi 1= welding position 8=current flux 9. What is difference between Welding and Brazing? Ans. In Welding concentrated heat (high temperature) is applied at the joint of metal and fuse together. In Brazing involves significantly lower temperatures and does not entail the melting of base metals. Instead, a filler metal is melted and forced to flow into the joint through capillary action.
Posted on: Thu, 22 Jan 2015 11:05:17 +0000
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