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Electric motors

Wed, 10 Feb 2010 04:35:37 +0100

Electric motors are everywhere! In your house, almost every mechanical movement that you see around you is caused by an AC or DC electric motor. By understanding how a motor works you can learn a lot about magnets, electromagnets and electricity in general. On this page we hope you will learn what makes an electric motor spin.
An electric motor is all about magnets and magnetism. A motor uses magnets to create motion. If you have ever played with magnets you know the law of magnets: Opposites poles attract and like poles repel. So if you have two bar magnets with their ends marked "north" and "south," then the north end of one magnet will attract the south end of the other. On the other hand, the north end of one magnet will repel the north end of the other. Inside an electric motor, these attracting and repelling forces create rotational motion.

The armature (or rotor) is an electromagnet. Like the Beakman rotor above made of copper wound in a circle, the motor below has copper wound around a soft iron core. The field magnet is still a permanent magnet, only this time there are two semi-circular magnets fitted inside a steel casing. In some larger motors and generators the field magnet could also be an electromagnet. In smaller motors it usually isn't to save the electricity that would otherwise be needed to make magnetism and also to reduce complexity. Actually, these days there are quite a few large motorsusing magnets to drive cars and the like. The Solar Navigator catamaran uses permanent magnet motors that are very efficient.

Generators

Wed, 10 Feb 2010 04:30:22 +0100

A simple generatoris similar to an electric motor.
With a motor, we put electrical energy in and get rotational energyout,
with a generator we put rotational energy in and get electrical energy out.

As with the motor, the current direction changes
with each half turn of the generator.
The generator produces alternating current
because slip rings are used in place of a split - ring commutator.

Skeleton system

Mon, 21 Dec 2009 04:02:20 +0100

Skeletons can be divided into two main types based on the relative position of the skeletal tissues. When these tissues are located external to the soft parts, the animal is said to have an exoskeleton. If they occur deep within the body, they form an endoskeleton. All vertebrate animals possess an endoskeleton, but most also have components that are exoskeletal in origin. Invertebrate skeletons, however, show far more variation in position, morphology, and materials used to construct them.

The vertebrate endoskeleton is usually constructed of bone and cartilage; only certain fishes have skeletons that lack bone. In addition to an endoskeleton, many species possess distinct exoskeletal structures made of bone or horny materials. This dermal skeleton provides support and protection at the body surface.
Various structural components make up the human skeleton, including collagen, three different types of cartilage (hyaline, fibrocartilage, and elastic), and a variety of bone types (woven, lamellar, trabecular, and plexiform). See also Bone; Collagen; Connective tissue.

The vertebrate skeleton consists of the axial skeleton (skull, vertebral column, and associated structures) and the appendicular skeleton (limbs or appendages). The basic plan for vertebrates is similar, although large variations occur in relation to functional demands placed on the skeleton.

Axial skeleton

The axial skeleton supports and protects the organs of the head, neck, and torso, and in humans it comprises the skull, ear ossicles, hyoid bone, vertebral column, and rib cage.

Skull

The adult human skull consists of eight bones which form the cranium, or braincase, and 13 facial bones that support the eyes, nose, and jaws. There are also three small, paired ear ossicles—the malleus, incus, and stapes—within a cavity in the temporal bone. The total of 27 bones represents a large reduction in skull elements during the course of vertebrate evolution. The three components of the skull are the neurocranium, dermatocranium, and visceral cranium. See also Ear (vertebrate).

The brain and certain sense organs are protected by the neurocranium. All vertebrate neurocrania develop similarly, starting as ethmoid and basal cartilages beneath the brain, and as capsules partially enclosing the tissues that eventually form the olfactory, otic, and optic sense organs. Further development produces cartilaginous walls around the brain. Passages (foramina) through the cartilages are left open for cranial nerves and blood vessels. Endochondral ossification from four major centers follows in all vertebrates, except the cartilaginous fishes.

The visceral skeleton, the skeleton of the pharyngeal arches, is demonstrated in a general form by the elasmobranch fishes, where all the elements are cartilaginous and support the jaws and the gills. The mandibular (first) arch consists of two elements on each side of the body: the palatoquadrates dorsally, which form the upper jaw, and Meckel's cartilages, which join ventrally to form the lower jaw. The hyoid (second) arch has paired dorsal hyomandibular cartilages and lateral, gill-bearing ceratohyals. This jaw mechanism attaches to the neurocranium for support. In all jawed vertebrates except mammals, an articulation between the posterior ends of the palatoquadrate and Meckel's cartilages occurs between the upper and lower jaws. The bony fishes have elaborated on the primitive condition, where the upper jaw was fused to the skull and the lower jaw or mandible could move only in the manner of a simple hinge. Teleosts are able to protrude the upper and lower jaws. In the course of mammalian evolution, the dentary of the lower jaw enlarged and a ramus expanded upward in the temporal fossa. This eventually formed an articulation with the squamosal of the skull. With the freeing of the articular bone and the quadrate from their function in jaw articulation, they became ear ossicles in conjunction with the columella, that is, a skeletal rod that formed the first ear ossicle. The remaining visceral skeleton has evolved from jaw and gill structures in the fishes to become an attachment site for tongue muscles and to support the vocal cords in tetrapods. See also Mammalia.

Vertebral column

The vertebral column is an endoskeletal segmented rod of mesodermal origin. It provides protection to the spinal cord, sites for muscle attachment, flexibility, and support, particularly in land-based tetrapods where it has to support the weight of the body. Hard, spool-shaped bony vertebrae alternate with tough but pliable intervertebral discs. Each typical vertebral body (centrum) has a bony neural arch extending dorsally. The spinal cord runs through these arches, and spinal nerves emerge through spaces. Bony processes and spines project from the vertebrae for the attachment of muscles and ligaments. Synovial articulations between adjacent vertebrae effectively limit and define the range of vertebral motion.

Vertebral morphology differs along the length of the column. There are two recognized regions in fishes (trunk and caudal) and five in mammals (cervical, thoracic, lumbar, sacral, and caudal), reflecting regional specializations linked to function. Humans have seven cervical, twelve thoracic, five lumbar, five (fused) sacral, and four coccygeal vertebrae. Most amphibians, reptiles, and mammals have seven cervical vertebrae regardless of neck length, whereas the number is variable in birds. Specific modification to the first two cervical vertebrae in most reptiles, birds, and mammals gives the head extra mobility. The presence of large ribs in the thoracic region often limits spinal flexibility. In typical tetrapods, the sacral region is usually modified for support of the pelvic girdle, while the number of caudal vertebrae varies greatly (from 0 to 50) between and within animal groups. See also Vertebra.

Sternum and ribs

Jawed fishes have ribs that help maintain the rigidity and support of the coelomic cavity. These ribs typically follow the connective tissue septa that divide successive muscle groups. In the caudal region, they are often small paired ventral ribs, fused on the midline to form the haemal arches. Ancestral tetrapods had ribs on all vertebrae, and their lengths varied between the vertebral regions. Modern amphibia (frogs and toads) have few thoracic ribs, and these are much reduced and never meet ventrally. Reptiles have varied rib arrangements, ranging from snakes with ribs on each vertebra (important for locomotor requirements) to turtles with only eight ribs which are fused to the inside of the carapace. Flying birds and penguins have a greatly enlarged sternum that links the ribs ventrally. In humans there are twelve pairs of ribs which form a strong but movable cage encompassing the heart and lungs.

Appendicular skeleton

This section of the skeletal system comprises the pectoral and pelvic limb girdles and bones of the free appendages. The girdles provide a supporting base onto which the usually mobile limbs attach.

Pectoral girdle

The pectoral girdle has both endoskeletal and dermal components. The dermal components are derived from postopercular dermal armor of primitive fishes, and are represented by the clavicles and interclavicles in modern vertebrates, except where they are secondarily lost. Endochondral bone forms the scapula. In fishes, the main component of the girdle (the cleithrum) is anchored to the skull by other bony elements. Increased mobility of the girdle is seen in amphibia as it becomes independent of the skull. Further development and skeletal reduction have resulted in a wide range of morphologies, culminating in the paired clavicles and scapulae of mammals.

Birds have fused their paired clavicles and single interclavicle to form the wishbone or furcula. Clavicles have disappeared in certain groups of bounding mammals to allow greater movement of the scapula. Although humans, and most other mammals, have a coracoid process on the scapula, other tetrapods typically have a separate coracoid bracing the scapula against the sternum and forming part of the glenoid fossa.

Pelvic girdle

The pelvic girdle forms by endochondral ossification, that is, the conversion of cartilage into bone. In the fishes, it is a small structure embedded in the body wall musculature just anterior to the cloaca. Each half of the girdle provides an anchor and articulation point for the pelvic fins. In tetrapods, the girdle attaches to the vertebral column to increase its stability and assist in the support of body weight and locomotor forces. Humans, like all other tetrapods, have a bilaterally symmetrical pelvic girdle, each half of which is formed from three fused bones: the ischium, ilium, and pubis. A part of each of these elements forms the acetabulum, the socket-shaped component of the hip joint, that articulates with the femoral head.

All urogenital and digestive products have to pass through the pelvic outlet. This accounts for the pelvic sexual dimorphism seen in most mammals, where the pelvic opening is broader in females, because of the physical demands of pregnancy and parturition. In birds (with the exception of the ostrich and the rhea), both sexes have an open pelvic girdle, a condition also found in female megachiropteran bats (flying foxes), gophers, and mole-rats.

Paired fins and tetrapod limbs

Paired fins in fishes come in different forms, but all are involved in locomotion. In the simplest form they are fairly rigid and extend from the body, functioning as stabilizers, but they are also capable of acting like a wing to produce lift as in sharks. In many fishes, the pectoral fins have narrow bases and are highly maneuverable as steering fins for low-speed locomotion. In addition, some fishes use their pectoral and pelvic fins to walk on the river bed, while others have greatly enlarged pectoral fins that take over as the main propulsive structures.

The basic mammalian pectoral limb consists of the humerus, radius, ulna, carpals, five metacarpals, and fourteen phalanges; and the pelvic limb consists of the femur, tibia, fibula, tarsal, five metatarsals, and fourteen phalanges. A typical bird pelvic limb consists of a femur, tibiotarsus (formed by fusion of the tibia with the proximal row of tarsal bones), fibula, and tarsometatarsus (formed by fusion of metatarsals II–IV), metatarsal I, and four digits (each consisting of two to five phalanges).

In biology, the skeleton or skeletal system is the biological system providing physical support in living organisms. (By extension, non-biological outline structures such as gantries or buildings may also acquire skeletons.)

Types and Classification

Skeletal systems are commonly divided into three types—external (an exoskeleton), internal (an endoskeleton), and fluid based (a hydrostatic skeleton), although hydrostatic skeletal systems may be classified separately from the other two, because they lack hardened support structures. An internal skeletal system consists of rigid or semi-rigid structures, within the body, moved by the muscular system. If the structures are mineralized or ossified, as they are in humans and other mammals, they are referred to as bones. Cartilage is another common component of skeletal systems, supporting and supplementing the skeleton. The human ear and nose are shaped by cartilage. Some organisms have a skeleton consisting entirely of cartilage and without any calcified bones at all, for example sharks. The bones or other rigid structures are connected by ligaments and connected to the muscular system via tendons.
Hydrostatic skeletons are similar to a water-filled balloon. Located internally in cnidarians (coral, jellyfish etc.) and annelids (leeches, earthworms etc.), among others, these animals can move by contracting the muscles surrounding the fluid-filled pouch, creating pressure within the pouch that causes movement. Animals such as earthworms use their hydrostatic skeletons to change their body shape, as they move forward, from long and thin to shorter and wider.

How did you add content to your web blog?

Mon, 21 Dec 2009 03:56:06 +0100

Very easy to add content to you web blog, just click on "Edit Menu" . On NAME write the name of the content you want it to be example " Mathematic".

How did you create a Google Map?

Sun, 20 Dec 2009 15:52:00 +0100

First, you need to sign up in Gmail. So you can get in to google map. Then you find the place you want to show on your website. Put the symbol in so people will know what the place is. Then click for a HTML code. Put the code in the blog in your website.

How did you create web widgets and web banners to your website?

Sun, 20 Dec 2009 15:48:44 +0100

Creating your own web widget isn’t hard to do using one of the many free widget services available - in fact, it can take as little as a minute! So what are web widgets and why use them?

Web widget is just a term for a syndicated content application drawing data from another site that can be embedded in a web page for display. When information is updated by the content provider, that update is reflected on all the sites using the widget.

If you run a blog or content site you can offer other webmasters a widget that will display the latest posts, articles, news and stories from your site. I’ve been doing this for quite a few years now with my article feed. It’s a very simple application that I update occasionally that delivers a full article on the sites that embed a snippet of code I provide (see end of post for link to the script).

Even if you don’t have a content oriented site, you can create widgets to deliver tips relating to the products and services you sell; and that can help draw people to your site when embedded on other sites.

As widgets have evolved and become more complex, the overhead associated with delivering the content has also increased. If you have a popular, intricate widget, it can bog down your server somewhat - and some hosts simply don’t allow for locally hosted widgets to deliver information to other sites through live syndication.

A plethora of widget providers have sprung up in recent years that will not only host your widget, but provide all the tools to create one.

It’s really easy to do - here’s one I created at WidgetBox that draws the headlines from this blog - it’s called a “blidget” and took all of about about 60 seconds to make.

What you learn about creating a website?

Sun, 20 Dec 2009 15:46:28 +0100

If you know how to create a website. It will be easy for you to look for a goog job. Many job in Thailand now really want a person who can create a website. I've learn many tecnique since I create a website in yola. I've know how to bring a world map to my website. How to create a wibgets. At first, I think I would be very bored because I'm not good at computer. But Teacher Simon teach us with his own tecnique that make students understand quickly. Create a website is not very hard as I think at first.

Plant cell

Sun, 20 Dec 2009 15:39:36 +0100

Plant cells are cells that are in plants. Plant cells are like animal cells, but they have a cell wall and chloroplasts. Here's a labeled picture of a plant cell. You will see all the main parts of the cell. Listed below are definitions of those words. Read on to learn more about photosynthesis.

A very special process that takes place inside of the chloroplasts in plant cells is called photosynthesis (foto-SIN-thi-sis). Photo means "light" and synthesis means " putting things together." In photosynthesis, green plants actually make their own food. That is so cool! Imagine if we could make our own food. I wonder what we'd make? Personally, I would make pizza. Plants seem to have the right idea since they make sugar. This amazing process is responsible for everything we eat. That's because animals eat plants, and we eat the animals and the plants.

If you would like to see an actual photograph of a chloroplast viewed through the lens of an electron microscope, visit the Nanoworld Image Gallery (you'll need to register in order to view the gallery).

In photosynthesis, the chloropyll (KLOR-a-fil) takes in energy from sunlight. The energy comes in the form of a tiny bundle known as a photon. The photon hits a molecule of water inside the chlorophyll. The photon's energy splits the water molecule into hydrogen and oxygen. The hydrogen combines with carbon dioxide (which the plant has absorbed from the air) to make sugars or glucose. The oxygen is released back into the atmosphere to give us more air. Did you know that the largest suppliers of oxygen in the whole world are tiny plants known as photoplankton? They are found in the oceans and are really important to giving us the oxygen needed to keep life going on our planet.

Believe it or not, a plant uses only about one-sixth of the energy it gets from the sun to nourish itself. The rest of the energy is stored in the glucose until it is eaten by other animals or humans. What an amazing process!

Trigonometry

Sun, 20 Dec 2009 15:37:52 +0100

The trigonometric functions (also called circular functions) are functions of an angle. They are used to relate the angles of a triangle to the lengths of the sides of a triangle. Trigonometric functions are important in the study of triangles and modeling periodic phenomena, among many other applications.

The most familiar trigonometric functions are the sine, cosine, and tangent. The sine function takes an angle and tells the length of the y-component (rise) of that triangle. The cosine function takes an angle and tells the length of x-component (run) of a triangle. The tangent function takes an angle and tells the slope (y-component divided by the x-component). More precise definitions are detailed below. Trigonometric functions are commonly defined as ratios of two sides of a right triangle containing the angle, and can equivalently be defined as the lengths of various line segments from a unit circle. More modern definitions express them as infinite seriesor as solutions of certain differntial equations, allowing their extension to arbitrary positive and negative values and even to complex numbers.

Trigonometric functions have a wide range of uses including computing unknown lengths and angles in triangles (often right triangles). In this use, trigonometric functions are used for instance in navigation, engineering, and physics. A common use in elementary physics is resolving a vector into Cartesian coordinates. The sine and cosine functions are also commonly used to model periodic function phenomena such as sound and light waves, the position and velocity of harmonic oscillators, sunlight intensity and day length, and average temperature variations through the year.

In modern usage, there are six basic trigonometric functions, which are tabulated here along with equations relating them to one another. Especially in the case of the last four, these relations are often taken as the definitions of those functions, but one can define them equally well geometrically or by other means and then derive these relations.

Animal cell

Sun, 20 Dec 2009 15:28:52 +0100

Animal cells are typical of the eukaryotic cell, enclosed by a plasma membrane and containing a membrane-bound nucleus and organelles. Unlike the eukaryotic cells of plants and fungi, animal cells do not have a cell wall. This feature was lost in the distant past by the single-celled organisms that gave rise to the kingdom Animalia. Most cells, both animal and plant, range in size between 1 and 100 micrometers and are thus visible only with the aid of a microscope.

The lack of a rigid cell wall allowed animals to develop a greater diversity of cell types, tissues, and organs. Specialized cells that formed nerves and muscles—tissues impossible for plants to evolve—gave these organisms mobility. The ability to move about by the use of specialized muscle tissues is a hallmark of the animal world, though a few animals, primarily sponges, do not possess differentiated tissues. Notably, protozoans locomote, but it is only via nonmuscular means, in effect, using cilia, flagella, and pseudopodia.

The animal kingdom is unique among eukaryotic organisms because most animal tissues are bound together in an extracellular matrix by a triple helix of protein known as collagen. Plant and fungal cells are bound together in tissues or aggregations by other molecules, such as pectin. The fact that no other organisms utilize collagen in this manner is one of the indications that all animals arose from a common unicellular ancestor. Bones, shells, spicules, and other hardened structures are formed when the collagen-containing extracellular matrix between animal cells becomes calcified.

Animals are a large and incredibly diverse group of organisms. Making up about three-quarters of the species on Earth, they run the gamut from corals and jellyfish to ants, whales, elephants, and, of course, humans. Being mobile has given animals, which are capable of sensing and responding to their environment, the flexibility to adopt many different modes of feeding, defense, and reproduction. Unlike plants, however, animals are unable to manufacture their own food, and therefore, are always directly or indirectly dependent on plant life.

Most animal cells are diploid, meaning that their chromosomes exist in homologous pairs. Different chromosomal ploidies are also, however, known to occasionally occur. The proliferation of animal cells occurs in a variety of ways. In instances of sexual reproduction, the cellular process of meiosis is first necessary so that haploid daughter cells, or gametes, can be produced. Two haploid cells then fuse to form a diploid zygote, which develops into a new organism as its cells divide and multiply.

The earliest fossil evidence of animals dates from the Vendian Period (650 to 544 million years ago), with coelenterate-type creatures that left traces of their soft bodies in shallow-water sediments. The first mass extinction ended that period, but during the Cambrian Period which followed, an explosion of new forms began the evolutionary radiation that produced most of the major groups, or phyla, known today. Vertebrates (animals with backbones) are not known to have occurred until the early Ordovician Period (505 to 438 million years ago).