Explanation | Units of Memory In A Computer | Learn About Computers |

Hello Everyone, Am Manjeet Singh and Today we will Discuss about Units Of Memory... So Let's Start...

Units of Memory:-

The memory unit is the principal storage of the computer. All the data and instructions that the 
computer needs at a moment are stored here. All storage devices are characterized with the following features:

1. Speed
2. Volatility
3. Access method
4. Portability
5. Cost and capacity

Linking Memory with the other units:

Basic Units of Measurement:

The components of the computer can recognize only two states that is presence or absence of an electrical signal. Two symbols used to represent these two states are 0 and 1, and are known as BITS (an abbreviation for BInary DigiTS). 0 represents the absence of a signal, 1 represents the presence of a signal. A BIT is, therefore, the smallest unit of data in a computer and can either store a 0 or 1.

Since a single bit can store only one of the two values, there can possibly be only four unique combinations:
00 01 10 11
Bits are, therefore, combined together into larger units in order to hold greater range of values. BYTES are typically a sequence of eight bits put together to create a single computer alphabetical or numerical character. More often referred to in larger multiples, bytes may appear as 

Kilobytes (1,024 bytes), 
Megabytes (1,048,576 bytes), 
GigaBytes (1,073,741,824), 
TeraBytes (approx. 1,099,511,000,000 bytes), or PetaBytes (approx. 1,125,899,900,000,000 bytes).

Bytes are used to quantify the amount of data digitally stored (on disks, tapes) or transmitted 
(over the internet), and are also used to measure the memory and document size.

Types of memory:-

Computers use several different types of memory. They are:

1. Main Memory/Primary Memory units:

– Two most important are

• RAM (Random Access Memory)
• ROM (Read-only Memory)

– They work in different ways and perform distinct         functions
– CPU Registers
– Cache Memory

2. Secondary Memory/Auxiliary Memory:

Also termed as ‘auxiliary’ or ‘backup’ storage, it is typically used as a supplement to main storage. It is much cheaper than the main storage and stores large amount of data and instructions permanently. Hardware devices like magnetic tapes, Floppy Disk, 
Hard Disk, Optical disks, Compact Disk (CD), Digital Versatile Disk (DVD) and Blu-ray Disc (BD) fall under this category.

Computer’s memory can be classified into two types – RAM and ROM.

RAM or Random Access Memory:

It is the central storage unit in a computer system. It is the place in a computer where the operating system, application programs and the data in current use are kept temporarily so that they can be accessed by the computer’s processor. The more RAM a computer has, the more data a computer can manipulate.

Random access memory, also called the Read/Write memory, is the temporary memory of a computer. It is said to be ‘volatile’ since its contents are accessible only as long as the computer is on. The contents of RAM are cleared once the computer is turned off.

ROM or Read Only Memory: 

It is a special type of memory which can only be read and contents of which are not lost even when the computer is switched off. It typically contains manufacturer’s instructions. Among other things, ROM also stores an initial program called the ‘bootstrap loader’ whose function is to start the computer software operating, once the power is turned on.

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Introduction to Computers | Anatomy of Computers | Input and Output Devices | Learn About Computers |

Hello Everyone, Am Manjeet Singh and Today we will Discuss about Introduction to Computers, Anatomy of Computers, Input and Output Devices... So Let's Start...

In human affairs we have reached a point where the problems that we must solve are no longer solvable without the aid of computers. I fear not computers but the lack of them. ISAAC ASIMOV

Introduction to Computers:

A computer can be defined as an electronic device capable of processing the data and producing the information.

The computer system essentially comprises three important parts –

1. input device,
2. central processing unit (CPU) and
3. output device.

The CPU itself is made of three components namely,

1. arithmetic logic unit (ALU),
2. memory unit, and
3. control unit.

Components of a computer system:

Central Processing Unit:

On broad basis, a computer performs the following tasks:

Input: 
Sending the data and command to the computer is known as input.

Processing:
Work done by the computer with the help of processing hardware and software to produce results is known as processing.

Output: 
The result displayed by the computer is known as output.

Storage:
A place to save result inside or outside the computer is known as storage.

Anatomy of Computers:
The following are the parts of a desktop computer.

Power Supply:

When you plug your power cable into your computer,
you are actually plugging into a socket in the power
supply unit that has been fitted inside your case. This
component is responsible for converting the 240 volt AC mains power to low voltage DC power needed by
computer components. The power supply generates
+3.3V, +5V, +12V, -5V. These voltages must be constant, right up to the maximum current your system
will draw under load.

Monitor:

Commonly known as a "screen," the monitor gives you a visual display of what your computer is up to. Monitor displays are divided into pixels. The higher the pixel count, the higher the "resolution." Resolutions are measured in Rows x Columns. Common resolution settings are 640 x 480, 800 x 600, 1024 x 768, 1280 x 1024, etc.

Mother board:

The mainboard I which is sometimes called a motherboard. This is usually the largest circuit-board in the computer, and every other component in the computer connects to it.

Central Processing Unit:

The Central Processing Unit (CPU)is usually called either a CPU or just a Processor. The CPU is the brain of the system. It executes all the program code from the operating system and the applications the user runs and processing of data. It sends CPU commands to direct the actions of all the other components in the computer.

Main Memory or Random Access Memory (RAM):

RAM, which stands for Random Access Memory, is the short term memory that the computer uses to keep track of what it's doing. If the computer loses power, anything stored in RAM is lost.

Storage Device:

Computer storage device is any type of hardware that
stores data. The most common type of storage device,
which nearly all computers have, is a hard drive.

INPUT AND OUTPUT DEVICES:

Input Devices:
Input device is a hardware device that sends information to the computer.

Mouse:

Mouse is a pointer device.The mouse allows an individual to control a pointer in a graphical user
interface (GUI). Utilizing a mouse a user has the ability to perform various functions such as opening a program or file and does not require the user to memorize commands.

Digital camera:

A type of camera that stores the pictures or video it takes in electronic format instead of to film.

Web Cam:

A camera connected to a computer that allows anyone connected to the Internet to view still pictures or motion video of a user.

Joystick:

A computer joystick allows an individual to easily navigate an object in a game such as navigating
a plane in a flight simulator.

Keyboard:

One of the main input devices used on a computer, a computer keyboard looks very similar to the
keyboards of electric typewriters, with some additional keys.

Microphone:

Sometimes abbreviated as mic, a microphone is a hardware peripheral that allows computer users to input audio into their computers.

Scanner:

Input device that allows a user to take an image and/or text and convert it into a digital file, allowing
the computer to read and/or display the scanned object.

Output Device:
Any peripheral that receives and/or displays output from a computer. Below are some examples of different types of output devices commonly found on a computer.

Monitor:

A monitor is a video display screen. Monitor is also called as Visual Display Unit (VDU) or Video Display Terminal (VDT).

CRT (Cathode Ray Tube) Monitors:

They are built very similarly to older (tube) television sets. They are heavy, bulky, take up a lot of desk space, and emit radiation.

LCD (Liquid Crystal Display) Monitors:

They are thin and flat. They are light, compact, take up very little desk space emit no known radiation.

Printer:

A printer is an output device responsible for
taking computer data and generating a hard
copy of that data.

Projector:

Speakers:

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Optical Activity | Physical Properties And Molecular Structure | Explained | Learn About Chemistry |

Hello Everyone, Am Manjeet Singh and Today we will Discuss about Optical Activity And Its Physical Properties And Molecular Structure... So Let's Start...

PHYSICAL PROPERTIES AND MOLECULAR STRUCTURE
 
The physical properties like density, optical activity, dipole moment, refractive index, magnetic susceptibility etc. can be determined quantitatively and play an important role in providing information about the molecular structure. 
The basic fact that these physical properties are additive, constitutive or both in nature helps us to determine the molecular structure.

(1) Additive property: The physical property the total value of which is equal to the sum of values of corresponding properties of the constituent atoms is called an additive property.
For example molecular mass of a compound.

(2) Constitutive property: The physical property which depends upon the constitution of the molecule i.e. the arrangement of atoms and bond structure in a molecule is called constitutive property.
For example optical activity, surface tension, viscosity.

(3) Additive and Constitutive property: If is defined as an additive property that also depends upon the arrangement and bond structure of atoms in a molecule.
For example surface tension, viscosity, magnetic susceptibility etc.

OPTICAL ACTIVITY

Some common terms: 

(1) Plane polarised light: A beam of ordinary light consists of electromagnetic waves vibrating in all planes perpendicular to its direction of propagation. When ordinary light is passed through a Nicol prism (a special type of prism made up of crystalline calcium carbonate) its vibrations in all directions except the direction of axis of the prism, are cut off. The emergent rays  come out with their vibrations only in one plane. A beam of light having vibrations only in one plane is said to be plane polarised light.

(2) Optical activity: If plane polarised light is passed thorough quartz or solutions of some substances like sugar, camphor, etc. the path of plane polarised light gets rotated. The substances which rotate the plane of polarised light are called optically active substances and the property of a substance to rotate the plane of polarised light is called optical activity. All optically active substances do not rotate there Plane of polarised light in the same direction. Some rotate the plane of polarised light to the right and are called dextro rotatory written as d or ( + ) as prefix to the name of the compound. On the other hand, the substances which rotate the  plane of polarised light towards left after called leavo rotatory written as l or( - ) as prefix to the name of the compound.

# The principle behind rotation of plane polarised light:

 
if two nicol prisms are placed with their polarisation planes parallel to each other, the planes polarised light emerging from first prism passes through the second and bright field is seen through the eye piece but if the second prism is turned through 90° so that the planes of polarisation of two prisms are at right angles, then the light rays coming out of the first prism are stopped by the second and a dark field is seen through the eye piece.

The first prism is called POLARISER and the second prism is called ANALYSER. If an optically active substance is placed between the polariser and analyser kept at dark field position some light starts coming through the analyser and the optical view appears some what bright. In order to get a complete dark view again, the analyser had to be rotated through an angle (alpha). From this observation it is clear that optically active substances has the power of rotating the plane of polarised light through a certain angle and hence it is said to be optically active.

To obtain dark view when the analyser is turned towards right( i.e. clockwise) the optically active substances is said to be dextro rotatory and when analyser is turned to left ( anticlockwise) the substances is called leavo rotatory.

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BLACK BODY AND BLACK BODY RADIATION | Explained | Learn About Chemistry |

BLACK BODY AND BLACK BODY RADIATION

Hello Everyone, Am Manjeet Singh and Today we will Discuss about Black Body And Black Body Radiation... So Let's Start...

To understand the concept of black body we consider

following two situation.

(1) Absorption of radiation by a body.
(2) Emission of radiation by a body.

When a radiation falls on the surface of a body, a part of it is reflected, some port of it is absorbed and the rest is transmitted. Whole of radiant energy is not absorbed because generally the surface of the objects are not perfect Absorbers of radiation. However if the radiation falls on a blackened metallic surface, it is almost completely absorbed. So, a body which completely absorbs all the radiations falling on it is called a black body.
Now we take the case of emission of radiation by the object. Radiation is emitted by any solid body at any temperature as a result of vibrations of its particles. At low temperature the emitted radiations are of low frequency. As the temperature is raised the emitted radiation goes from a lower frequency to the higher frequency. Different solids emit radiation at different rates at same temperature, the emission rate is maximum when the solid is perfect black. In other words, when a body is heated, it radiates maximum amount of radiant energy. So a black body is a perfect emitter of radiant energy. At a given temperature, a black body radiates maximum amount of radiant energy. Thus a black body is defined as an object that  completely absorbs all the radiations falling on it, it is also a perfect emitter of radiation.
The radiation emerging from a black body is called " black body radiation". 

Experimentally, a nearest approach to black body is a hollow sphere blackened from inside and having a small hole for the entry of radiations. The inner surface of the sphere is blackened with lamp black. This blackened surface helps in complete absorption of radiations falling on it. The black body designed by Fery is shown in figure. It consists of a hollow double walled metallic sphere having a hole. The inner surface has a projection to prevent the direct reflection of the radiations entering from the hole. The inside surface is blackened with lamp black. Its exterior is completely insulated from surroundings so as to avoid the loss of radiation in the form of heat. Any radiation that enters black body through a small hole is reflected repeatedly from the walls and reabsorbed inside the sphere untill all of the energy is absorbed.

When a black body is heated, it glows from inside and cannot lose any energy to the outside world. It soon attains a state of thermal equilibrium and no external heat energy is required to maintain a constant temperature. But the inner walls are radiating all types of wavelength. The radiation emitted by a black body at a particular temperature are called Black Body Radiation. The origin of these black body radiations lies in the vibrations of particles of the body ( the oscillators) that emit the radiation energy in the form of electromagnetic waves.

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What is Dipole Moment And Dipole Field?? Explained

Hello Everyone, Am Manjeet Singh and Today we will Discuss about Dipole Moment And Dipole Field... So Let's Start...

Dipole Moment: Dipole Moment (p) is a measure of the strength of electric dipole. It is a vector quantity whose magnitude is equal to protect of the magnitude of either charge and the distance between them.

i.e.      p=q(2a)     or      |p|=q(2a)

By convention, the direction of p is from negative to positive charge.
Then SI unit of dipole moment is coulomb-metre (C-m)
If charge q gets larger, and the distance 2a gets smaller and smaller, keeping the product |p|=q×2a=constant, we get what is called an ideal dipole or point dipole. Thus, an ideal dipole is the smallest dipole having almost no size.

Physical Significance of electric dipoles...
The study of electric dipoles is important for electrical phenomena in matter. Matter, as we know, consists of atoms or molecules which are electrically neutral. In a molecule, there are positively charged nuclei and negatively charged electrons. If the centre of mass of positive charges coincides with the centre of mass of negative charges, the molecule behaves as a non-polar molecule. On the contrary, if the centre of mass of positive charges does not coincide with the centre of mass of negative charges, the molecule behaves as a polar molecule and it possesses some intrinsic or permanent dipole moment. In the absence of an external electric field, the dipole moments of different molecules in a piece of matter are randomly oriented, so that net dipole moment of the piece is zero. When an external electric field is applied, the polar molecules tend to align themselves along the field and some net dipole moment developes. The piece of matter is said to have been polarised.

When non-polar molecules are subjected to the action of an external electric field, the centres of mass of positive and negative charges in the molecule get displaced in opposite directions. Thus, the external field induces some dipole moment in the molecule in the direction of the field. The induced dipole moments of different molecules in the sample add up vectorially to produce some net total dipole moment.

Dipole Field: The Dipole field is the electric field produced by an electric dipole. It is the space around the dipole in which the electric effect of the dipole can be experienced. The electric field of the pair of charge (-q and +q) at any point in space can be found from Coulomb's law and the superposition principal. To calculate dipole field intensity at any point, we imagine a unit positive charge held at that point. We calculate force on this charge due to each charge of the dipole and take vector sum of the two forces. This gives us dipole field intensity at that point. We shall show that though the total charge of electric dipole is zero, the field of the electric dipole is not zero. This is because the charge q and -q are separated by some distance. The electric fields due to these charges, when added, do not cancel out. However, at distances much larger than the separation of two charges, i.e., r>>2a, the fields due to q and -q largely cancel out. Therefore, at large distances from the dipole, the dipole field falls off more rapidly than like E~1/r² for a point charge.

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