Thursday, January 29, 2015

What is global warming?Explan

As we said above, the vast amount of man-made gases are buildig up a layer, like a blanket

Thursday, January 22, 2015

the energy saving home

combining solar power with the skilful use of insulating materials should lead to the building pf houses that use very little,if any, other form of heating .
solar panels on the roof are positioned to catch as much sunlight aspossible.these will providewarm water which can be stored in insulated tanks.
large double(or triple)glazed windows are positioned on the side of the house with most sunlight and small windows elsewhere.
agreenhouse or conservatory is built no the sunny side of the house.the warm air from rir from here can be circulated around the house.

Sunday, January 18, 2015

the using electromagnets

electromagnets are used in many domestic and industrial devices. they are used for lifting, sorting and moving objects as well as for recording information. for an electromagnets to do a useful job, it needs to produce a very strong magnnetic field.

electromagnets have a coil of  copper wire wound tightly around an iron core   using  iron in the core makes the magnet 2000 times stronger then the  same solesoid with nothing but air inthe core.whenthe current in the coil is switched on, the magnetic field of the solenid magnetizes the iron, which has a much stronger magnetic fieldthan the solenoid on its own. another advantage of using iron is thet the core loses its  magnetism as soon as the current is turned off. iron is asoft magnetic material.

electromagnts can be used to separatr ferrous metals like iron and steel from non-ferrous metals like copper and aluminium. they are also used in many other devices sush as loudsspeakers and electric motors.

Friday, January 16, 2015

what is refraction of light?

light travels at almos 300,000 km/s in air but slow down when it enters a diffrent materil such as water or glass.if a ray of light meets the new materail at an angle ,it bends. this bending is called refraction

as it leaves  the glass it speeds up again and so bend away from the normal. the ray emerging from this ractangular block is parallel to the ray going  in.

refrraction in different materials

when light enters amterial at an angls,it changes direction becuse its speed changes. if the material is very dense,the light slows down more and so the refraction is graeter.

apparent depth  one of the effects of refractionis that the brain can be tricked into thinking that things are in a different place from where they really are. fish can compensate for refraction between water and air. this is how they can catch insects at the surface and avoid predators such as herons.                                                                                                              

Wednesday, January 14, 2015


a hundred years ago there were probably fewer people in the world than there are in pakistan alone today.  the population of the earth in 2007 was about 6,500,000,000, (6.5billion) scientists estimate that by 2050 it will have risen to 10,000,000,000 (10 billion) this creates very serious problemes for our environment.

two to three thousand years ago, most of the population of the world lived in small villages, with a few relatively larger towns the only smoke was from fires for heating and cooking. much of the world was covered with forests, and trees were cut down only for fuel and for building huts.

there was no waste from food, no paper,on tin cans or bottles-apart from bones and other inedible parsts houseehold goods were simple and usualllasted a lifetime, and as they were made of wood, they could burned when no longer of use. sewage and manure were saved and used as fertilizer for the land..

Tuesday, January 13, 2015

stroy of allama iqbal (1877-1938)

allama iqbal was the great poet  and philosopher who,perhaps more than any other single person apart from m.a.jinnal, was responsible for the state of pakistan.

he was a brilliant scholar, studying philosophy and law in in england, and then in germany. back in india, he practised law, and became the greatest urdu poet of his age later, his poetry became  away of putting forward his reltical and political ideas_much of his poetry was written inpersian, so that it would be widely understood throughout the muslim world.                                                                                                                                                                                                                                                                            aas early as 1910,iqbal throught that the  muslim world should be united. his poems pointed to the glories of islam in the past aand the miserable state it was in at the time .he called for ref