MAGLEV TRAIN

MAGLEV TRAIN.

Maglev Train is a Magnetic Levitated 

( no friction ) train. 

If you ever played with magnets , you know that unlike poles attract each other and like poles repel each other.

This is the basic principle behind Maglev Trains.

In Maglev Trains there are strong electromagnets attached at the bottom of the train ( i.e ;- at the place of wheels ) and also at the place of railway tracks.

These electromagnets produces a repulsive action and hence makes the train at some distance above from the tracks.

The big difference between Maglev train and conventional trains is that Maglev trains do not have an engine and wheels.

But it has a source which produces thrust energy for its forward movement ( e.g ;- big fan ).

Because of the elimination of wheels and rail tracks and also because the train is at some distance above from the tracks , there is no mechanical friction and hence energy losses are minimized.

At present Maglev Trains are the fastest trains in the world with a top speed of 430 km/h.

HOW DOES YOUR REFRIGERATOR WORKS?

HOW DOES YOUR REFRIGERATOR WORKS?

How your refrigerator cools the food you put inside it ?

This is a good practical example of the gas laws in action.Temperature , Pressure and Volume all have a part to play in the cooling process.

Firstly , Gas ( generally Ammonia ( NH3 ) ) is drawn at low pressure and low temperature through a line.

The gas is compressed using electricity to a higher pressure and its temperature rises  ( just like a bicycle pump which gets warmer when you are pumping up a tyre.

It is then transferred to a condenser where the heat is removed and the gas begins to condense into a liquid.

The heat is released via cooling fins on the back of the refrigerator unit.

The liquid then goes through an expansion device where its pressure is suddenly lowered , it expands and some of the liquid turns very quickly into vapours.

This change of state has a cooling effect.Now the cold vapour and vapours are able to cool the air in the cabinet of the refrigerator through an evaporator.

The cold liquid absorbs the warmth or heat from the air inside the refrigerator and turns back into a low temperature gas , at low pressure.

It now starts its journey again through the compressor.

MODES OF HEAT TRANSFER.

MODES OF HEAT TRANSFER

Firstly , when a temperature difference occurs between two bodies or a body with its surroundings , heat transfer occurs.
There are basically three modes of heat transfer :--

(1.) Conduction  :-- Conduction is mode of                                      heat transfer in which heat                                is transferred via direct                                             contact.
For e.g  :-- If we touch a hot plate or pot , we are going to feel the heat because we are touching it , its because of direct contact and is due to conduction.

Conduction generally occurs in solids and liquids.
In conduction heat is transferred due to the vibrations and collisions between the medium particles which occurs due to the source of heat.

(2.) Convection  :-- Convection is the transfer                               of heat due to the actual                                   movement of the medium                                 particles.

Convection generally occurs in fluids ( liquids and gases ).

For e.g :-- When a liquid is heated it expands                  and this lowers its density.
The less dense liquid rises and its place is taken by more dense colder liquid.
This movement of liquid is responsible for the heat transfer and this is the basic principle behind convection.

(3.) Radiation  :-- Radiation is the transfer of                               heat via indirect contact or                               not touching.
It is basically heat travelling through air or space.
It is also described as the flow of heat from one place to another by means of electromagnetic waves.
It is very common because it is the primary method of heat transfer like in case of fire and sun.

For e.g :-- If we sit near fire we feel warmth , it is due to radiation.

BAGGER 293 ( World's largest bucket wheel excavator

BAGGER 293 ( World's largest bucket wheel excavator )

Bagger 293 is the world's largest bucket-wheel excavator built in Germany in 1995.

It is about 315 foot tall , 750 foot long and weighing over 31 million pounds.

It requires a crew of five to operate and can move over 8.5 million cubic feet of earth per day , to put that in perspective , that is the equivalent of digging a hole of the length of of a football field and over 80 foot deep in a day.

Its first name was MAN/TAKRAF RB293 given by the manufacturers they built it.

For the excavation the Bagger 293 uses a large 70 foot rotating wheel at the end of a long arm.

The wheel has a series of buckets attached  , and as the wheel rotates the buckets pick up the earth and dump it onto a conveyor belt.

The conveyor belt will transport the earth to other vehicles for removal to the dumping site.