EME

Why is it called compression ignition engine?

examfobia — Sat, 17 May 2008 12:44:26 +0000

In this type of engine, combustion takes place due to compression of gases. So, it is called a compression ignition engine.

Whereas the other one i.e. spark ignition engine, here for the combustion to take place, spark is used.

What is a gudgeon pin?

examfobia — Mon, 05 May 2008 05:33:43 +0000

In internal combustion engines, the gudgeon pin is that which connects the piston to the connecting rod. The gudgeon pin is typically a forged short hollow rod made of a steel alloy of high strength and hardness that may be physically separated from both the connecting rod and piston or crosshead.

Why glass is provided in vegetable compartment in a fridge?

examfobia — Wed, 09 Apr 2008 09:41:42 +0000

To keep the vegetables fresh, it should contain moisture. So. if a glass is provided above it, then the vapour particles leaving the vegetables will strike the glass and return backand keep the vegetables fresh. Here, instead if a plate with holes would have been provided then vapour particles would not return back and the vegetables will dry.

And the main reason is if we don’t provide this plate the vapour particles goes to the freezer where there will be problem in freezing due to vapour particles i.e. freezing will not take place upto appropriate level.

What is the difference between sensible heat and latent heat?

examfobia — Tue, 08 Apr 2008 07:03:13 +0000

The heat required to change the phase of a substance without the change in temperature is called latent heat. i.e. the change from 100% solid at 0 degree to 100% liquid at 0 degree.

The heat required to increase the temperature of a substance without the change in phase is called sensible heat. i.e. the change from 100% liquid at 0 degree to 100% liquid at 100 degree.

How bike’s engine starts working when switch tirns from off position to on position?

examfobia — Sat, 15 Mar 2008 05:51:45 +0000

As the switch turns on the battery produces a spark which ignites the fuel. This fuel pulls the piston down. Then the piston-cylinder cycle starts as in general and the bike starts. The main point is the spark produced when switch turns on.

Why six stroke engine are generally not used in two-wheelers?

examfobia — Sat, 15 Mar 2008 05:45:17 +0000

In a six-stroke engine six strokes would give one power output which is not preferable,and three cylinders will be required which will make the device bulky.Also for less power more fuel is required here as more power is not required in two wheelers.It also cannot carry such large engine. A twowheeler requires a small engine so, such six stroke engine is not generally used.

SYLLABUS >>> EME

examfobia — Sat, 15 Mar 2008 05:31:17 +0000

3- PROPERTIES OF GASES

5-HEAT ENGINES (UPTO 5.7)

BOILER MOUNTINGS & ACCESSORIES

11- AIR COMPRESSOR

Why compressors are used in refrigerating systems?

examfobia — Tue, 11 Mar 2008 07:57:48 +0000

To remove the vapour from the evaporator and to raise the temperature and pressure of the vapour to a point such that the vapour can be condensed wiyh normally available condensing media.

In short, to increase the pressure(above atmospheric pressure) and temperature compressors are used. This refrigerant(which comes out of compressor) which has high pressure,temperature and is in vapour form when enters the condensor changes to liquid form.

what is the physical meaning of enthalpy?

examfobia — Mon, 10 Mar 2008 10:45:19 +0000

Enthalpy is a thermodynamic function of a system, equivalent to the sum of the internal energy of the system plus the product of its volume multiplied by the pressure exerted on it by its surroundings. The term enthalpy is composed of the prefix en-, meaning to “put into” and the Greek word -thalpein, meaning “to heat”, although the original definition is thought to have stemmed from the word, “enthalpos” . It is often calculated as a differential sum, describing the changes within exo- and endothermic reactions, which minimize at equilibrium. In thermodynamics and molecular chemistry, the enthalpy or heat content is quotient or description of thermodynamics potential of a system, which can be used to calculate the useful work obtainable from a closed thermodynamics systems under constant pressure.

why does the injector is provided in diesel engine?and why carbeurator is provided in petrol engine instead of injector?

examfobia — Fri, 07 Mar 2008 04:42:24 +0000

A diesel engine uses compression ignition, a process by which fuel is injected after the air is compressed in the combustion chamber causing the fuel to self ignite. By contrast, a gasoline engine utilizes the Otto cycle, in which fuel and air are mixed before entering the combustion chamber and then ignited by a spark plug.