SPORTS & GAMES:

Sports and games are very important for us .They are essential for character building. In the developed countries like England sports and games are the part of education.

There many training centers for games and sports in these countries.

sports and games are becoming popular Pakistani school as well. Pakistani school boys and girls know the importance of sports and games.

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 In Door & Out Door Games: 

Hunting , fishing ,riding  etc are general sports but football, hockey,cricket ,tennis ,badminton are very popular in school and colleges.Thousand of students takes part in these sports and games. sports and games make school life colourful.

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Communication Network Components

Communication Media:
Communication media communication is used to transfer data from a computer to an computer computer. Low cost LAN are connex ted with twisted wire pair, many LAN, you can use the tibet optic cables. These cables are expensive but prov ile faster communication. Some 1 ANS kls use wireless transmission media. It is infected with USB infrared or wavs to countest computers off. Wireless networks are easy to setup and maintain Horever, tie has low transmission   and limited distance between two communication devices.

 

NIC:

It is also known as IAN adapter Lets smission used to be a computer to a network. It is a circuit board installed on the motherboard a lim Nowadays most computer systems have mother board in a network card bult. Wireless network card is antenna that sends and receives data

BRIDGE:

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Bridge A network bridge can be used in network networks to connect to two LANs and to the network. Separate network segments A segment is a part of a network when a bridge receives a signal, it determines the segment where the signal should be sent. If you are not sure what you want to do, then you will be able to communicate with your computer.

The Router :
A Router is a communication device Connect multiple networks using similar or different protocols. It manages the best route between the two routine users in the Li Routers used when multiple networks are connected. A router can be used on a network of any size. It can connect networks of different countries. They transfer data in less time. The router is an intelligent device. It uses algorithms to find out the best way to transfer
for data to a network.

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Video Display Adapters

Video Display Adapters:
                                                              A video display adapter must be attached to the computer to display graphics. It is also called video graphics card It is a circuit board that determines the following things Screen Resolution The number of bits used to store color information about each pixel called bit depth The total number of colors that can be used to display images Speed with which images appear on the display screen.

Types of Video Display Adapters:
Different types of video display adapters are as follows:

1VGA:
VGA stands for Video Graphics Array. It supports 16 to 256 colors depending on ii. Gas This screen resolution It supports 16 colors at 320-200 pixels. It supports 256 colors at 640k840 pixels. It is called 4-bit color.

2. SVGA:
SVGA stands for Super Video Graphics Array. It supports 256 colors at higher resolution then VGA It has two graphics modes. These are 800x600 pixels and 1024x768 pixels. It is called 8-bit color. SVGA is the most common standard used today. It is used primarily with 15-inch monitors.

 

3XGA:
XGA stands for Extended Graphics Array It supports up to 16.7 million colors at a resolution of 1024 768 pixels. It is called 24-bit color or true color. It is used with 17 and 19 inch monitors.

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Fission Chain Reaction

Fission Reaction Chain:

We know that during a fission reaction a nucleus of U-235 absorbs a slow neutron and breaks into of almost equal masses along with the emission of 2 or 3 neutrons. By properly using these neutr reaction can be produced in more Uranium atoms such that a fission reaction can continuously ma This process is called Fission Chain Reaction. There are two types of Fission Chain Reaction. two maintain itself.
. Uncontrolled Fission Chain Reaction:

1 41 when U is bombarded with a slow neutron, then Ba and Kr are formed and three neutrons are emitted. These 3 neutrons cause three more fission reactions in three u atoms and g neutrons are produced These 9 neutrons will cause additional fission. In this way the process multiplies and is called Uncontrolled Fission Chain Reaction as shown in 92 235 92 figure. This is principle of atom bomb. As a result of uncontrolled fission chain reaction in an atom bomb an atomic explosion takes place and a huge amount of energy is released.




 2. Controlled Fission Chain Reaction: 
It is possible to produce such conditions in which only 1 neutron out of all the neutrons produced in one fission, produces further fission. The other neutrons either escape out or are absorbed in some other medium except uranium. Such a reactions is called controlled fission chain reaction and fission reaction proceeds with constant initial speed. 235  a slow neutron is incident on a thin sheet of U.
Fission Takes Place:
Fission takes place but three neutrons produced are scattered into air so no further 92 fission can take place.  only two fission reaction take place. No further fission is possible. Hence, chain reaction is not possible. 235 in Fig. (c) if the sphere of is big one, then most of the neutrons produced due to fission reaction get absorbed in U before escaping out 92 92 of the sphere and produce a chain reaction. Critical Mass: The minimum mass of uranium which can sustain a chain reaction is called the critical mass. Critical Volume: Volume of the critical mass of Uranium is called critical volume. Reaction between Mass of Uranium and Critical Mass: If the mass of uranium is

much greater than the critical mass, then the chain reaction proceeds at a rapid speed and a huge explosion is produced. Atom bomb works at this principle.

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Production of X-Rays

Production of X-Rays:
                                                           

Production of X-Rays:

X-Rays were discovered by Germen physicist. X-Rays have very smaller wave length or high frequency . The production of X-Rays

 is the reverse process of photo electric effect.

X-Rays:

Then fast moving electrons strike  on a metal surface photo of very high energy are emitted known as X-Rays.

Ka Rays:

Suppose that a fast moving electron of energy Ve strike target of tungsten or any other heavy atom . Let an Electron from K-Shell of the atom is Removed it produce a Vacancy of electron or hole in k shell.

The electron from Lshell jumps to occupy the hole there by  the emitting a photon energy.

K         

      B Rays:

It is possible that electron jumps from M- shell in to K- shell. The  Photon emitted with energy.

Biological Effects of X- Rays :

OGICAL EFFECTS OF X-RAY/Side X ( y are Ionizing radiations. They may cause damage to living tissue As always photons are absorbed in tissues they break molecular bonds and  the molecular structure of proteins and especially the genetic y excessive use. Even when the organism itself shows no apparent e highly reactive free radicals (such as H and d rial. Young and rapidly growing cells are sensitive, hence X-fays are  for selective destruction of cancer cells. The X-ray can cause cancer asi se. damage, excessive use may cause the changes in reproductive system that will affect the organism 's offspring ICO' will Production of x rays can be regarded as the inverse of (a) Fair production (b) Compton effect ey Photo electric effect.

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Experiment to produce induced EMF and Current

Description:
Consider a straight piece of wire of length in magnetic field of a permanent magnet . The wire is connected with a sensitive   galvanometer. so it forms a closed loop without battery.
Induced Current:
When we move the loop from left to right a current flow in the loop . The current stops when the loop stops to move. Now, if we move loop in opposite in direction current also in the reverse direction.

Induced Emf:
If we change the resistance of the loop by inserting different resistor in the loop and move it in uniform magnetic field with same velocity then the product of the induced current and resistance of the loop remain constant.

Conclusion:
Relative motion of the loop and the mognet produces Induced emf in the loop, In mf is produced Greater the rate of change of magnetic flux, larger is the alvanometariment we use a bar magnet and a coll to which a sensitive.

 Case- In 1:
 Induction due to Motion of Magnet) galvanometer is connected as shown in galvanometer en there is no relative motion between magnet and coll then shows no current.
Case- II :
When the b ote bar magnet is moved towards the coll,the magnetic flux changes and a current is Induced in the coll.
 Case- III :
When the bar magnet Is moved away from the coil, the magnetic flux changes and a current is Induced in the coil in opposite direction Alternate Method This experiment can also be performed by moving the coil towards or away from the magnet.
Experiment No.3:
induction due to Changing the Area of Coil) In this experiment we can produce the induced current by changing the area of coil in uniform magnetic field, as shown in figure When the coil is being distorted so as to reduce its. area an emf and hence current appears. The induced current disappears when there will be no change in area. When the distorted col comes to its original circular shape thereby increasing the area, the induced current is produced but opposite in direction This current lasts as long as the area is changing.

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In the Street of the Fruit Stalls

Description:
In the Street of the Fruit Stalls
Wicks balance flame, a dark dew falls
 In the street of the fruit stalls .
Melon, guava, mandarin,
Pyramid-piled like cannon balls
Glow red-hot, gold-hot, from within.
Dark children with a coin to spend
 Enter the lantern's orbit; find
Melon, guava, mandarin-
The moon compacted to a rind,
The sun in a pitted skin.
They take it, break it open, let
A gold or silver fountain wet
 Mouth, fingers, cheek, nose, chin:
Radiant as lanterns, they forget
The dark street I am standing in.

Theme:

This is a symbolic poem. The world is threatened with war. enjoy the poverty. But all these have failed to crush man's love for pleasure. Childre sweet spray of the juice forgetting all about the misery they live in Paraphrase It is evening time. I t is wet and dark. There is a street of fruit sellers where various fruit are piled up in a conical form. They reflect hot, red and golden colours which in dim lantern light look like bombs. Poor children come there with a coin and stand in the light of the lanterns. They look at melon, guava and other fruit. Their mouths water. They pick up a fruit and break it open. Juice comes out and pours itself into their mouths, and also sticks on their fingers and cheeks. They enjoy the fruit, and are least conscious of their surroundings.

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