You might think that batteries are a modern invention, but batteries were one of the first ways of making electricity. Alessandro Volta discovered the first electric battery in 1800. He made a giant stack of alternating layers of zinc, blotting paper soaked in salt water, and silver. This early design for a battery became known as the voltaic pile.

How does a voltaic pile make electricity? The key to electricity is the movement of particles carrying electric charge. In a voltaic pile, these particles move from one metal to the other through a solution called the electrolyte. An electrolyte is a liquid that contains particles carrying charge. Dissolved salt is an example of a good electrolyte. The charged particles in the electrolyte react with the metals, causing an electrochemical reaction, a special kind of chemical reaction that makes electrons. As electrons are particles that carry electric charge, making these electrons all move in the same direction will create a electric current or electricity. You can read more about the basics of electricity in the Science Buddies Electricity, Magnetism, & Electromagnetism Tutorial.

The two types of metals in a voltaic pile are called electrodes. As the types of metal are different, one metal will like to give off free electrons, the other will be more eager to receive electrons. This creates an electrical potential difference, also called voltage between the two types of metals. One metal becomes positively charged (the positive electrode) and the other becomes negatively charged (the negative electrode). This voltage causes electrons to move, creating an electrical current, and then you have electricity!

In this experiment, you will make your own version of the voltaic pile using two different types of coins (two different kinds of metal) and a salt-vinegar solution (the electrolyte). The metal in the coins will react with the electrolyte. As the two metals are different, one metal will like to give electrons to the other, creating electricity. How will different numbers of coins affect the amount of electricity produced? To test this, you will make piles with different numbers of coins and measuring the voltage (measured in Volt) and current (measured in Ampere) produced.

Electric charge	electromotive force or potential difference expressed in volts.
Electrolyte	a conductor, not necessarily metallic, through which a current enters or leaves a nonmetallic medium, as an electrolytic cell, arc generator, vacuum tube, or gaseous discharge tube
Electrochemical reaction	a flowing, a flow
Electrons	an elementary particle that is a fundamental constituent of matter
Current	any process either caused or accompanied by the passage of an electric current and involving in most cases the transfer of electrons between two substances—one a solid and the other a liquid.
Electrode	any substance that dissociates into ions when dissolved in a suitable medium or melted and thus forms a conductor of electricity.
Voltage	one of the basic properties of the elementary particles of matter giving rise to all electric and magnetic forces and interactions.

Answer the Questions

What materials can a battery be made out of?

Why is it important for the materials to be arranged in alternating layers?

What does the electrolyte solution do?

Will more layers make a more or less powerful homemade battery?

Skeletal System

The skeleton is a system of bones connected in different ways. The type of joints used to connect bones in a certain part of the body determines the kind of movement. The joints of the skeletal system are divided into two major categories: movable and immovable. Most of the joints of the skeleton are movable. There are four basic kinds of movable joints in the human skeleton.

You can move your arm in a circle because your upper armbone is connected to your body at the shoulder by a ball-and-socket joint. The largest movable joint in the skeleton has two functions: It allows a bone to turn freely in any direction and to support heavy weights.

Your elbow can move in only one direction. It is a hinge joint. More than sixty joints of the body are hinge joints. For example, the knee, the toe and finger joints. Hinge joints are located in the skeleton where there is movement in only one direction.

The pivot joint is the only one of its kind in the body. The pivot joint is formed by the first two vertebrae of the spine, the atlas and the axis. The atlas supports the skull. The axis is underneath the atlas. The axis has a small structure which projects up through a hole in the atlas.

In the gliding joints the bones rest against each other and move sideways and up and down, gliding across one another. Gliding joints (in your wrists and ankles) cannot move as freely as other movable joints.

Some of the bones provide protection for the internal organs. These bones are fused together in fixed, immovable joints to form a protective shield. Five bony plates of the skull are fused together to form an immovable joint.

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Skeletal System Facts

When human infants are born, their bodies contain as many as 300 to 350 bones but, later on, as the developmental processes proceed there also occurs the fusion of these bones. Consequently, as a child reaches the age of 9, only 206 bones are left behind, and this number remains intact throughout the periodsof youth, adulthood and old age. As is the matter with any other organ system in your body, the human endoskeleton does have a number of different constituents which are in the first place classified on the basis of their position and structural or functional peculiarity in the body. In this way, as an advanced level learner, you can say that axial and appendicular are the two major divisions which do have extensions or further subdivisions as described below:

Axial Human Skeleton

As the very name suggests, you can immediately realize that the constituent parts of this division are positioned along the axial plane of the body and include vertebral column, cranial structure and the rib fence.

Vertebral Column

Extending from the pelvic province to the cervical sector, this is the lower most part of your skeletal subdivision and is formed by the joining of smaller compact units closely placed and interlocked together to give you the best possible level of support and posture you want. Interestingly, it is the characteristic construction which renders the cognomen "vertebrates" to the living creatures which possess it, while those devoid of it have the sobriquet "invertebrates". The spine or backbone in Home sapiens is subdivided into as many as thirty-three (33) individual units or vertebrae out of which two dozen (24) are the articulating ones while the remaining nine are relatively fused, thus giving rise to the sacrum and the coccyx.

Rib Cage

As we started from the lower position and are moving upwards, the second major division of your axial skeleton is that of the rib cage which, as the very name suggests, is a hollow cage-like bony and cartilaginous construction found in your chest region. Owing to its strategic positioning in the thoracic region, the learners and instructors alike prefer to call it the thoracic cage. This core portion of your human skeleton is surrounding the thoracic cavity and supports the pectoral girdle. If you want to have how-know about its further subdivision, the anatomists are there to guide you who distinguish its constituent parts into a dozen thoracic vertebrae, two dozen ribs, sternum and the costal cartilaginous structures.

The Skull

You shouldn't have any doubt about the established doctrine that human skull is one of the hardest and most important bony configurations in the body as it surrounds and safeguards the master/chief organ brain. On the basis of embryological origin, you can easily systematize the skull of an adult human fellow into two distinguishable categorical parts, which are named as neurocranium and viscerocranium. Here the former is assigned the responsibility of shielding and looking after the brainy contents including the brain stem, whereas the latter is concerned with the formation of facial skeleton to configure and maintain the shape of the face.

Appendicular Skeleton

As you have already been briefly informed, it is the second principal division of the human skeleton which is attached, at various points, to the axial skeleton to form the accessory or supporting structures. With the overall composition of over hundred (approximately 126) bones in your body, for the sake of convenience, it is broadly grouped into six constituent classes, namely, the pectoral girdles, the pelvis, arms & forearms, hands, thighs & legs, feet and ankles.

The Pectoral Girdles

Also termed as shoulder girdles, these are two in number (corresponding to the number of shoulders you have) and serve as connecting structures between the upper limbs and the axial skeleton on each side of your bilaterally symmetrical body. Regarding configuration, each of these girdles consists of two structural components, called scapula and clavicle, which on one hand are connected with the proximal end of the humerus and, on the other hand, make junction with the axial skeleton. As a result of this specific arrangement of bones, an articulatory junction is formed which you term as sternoclavicular articulation.

The Pelvis

The two bones, connected to the left and right of hip, are collectively known as the pelvis, which is an important part of the Homo sapiens' skeletal system found between the thighs and the abdominal region. The skeleton, embedded in this region, is sometimes also pronounced as the pelvic skeleton or even the bony pelvic and consists of the pelvic cavity, floor and the perineum (located below the pelvic floor). It is noteworthy that your pelvic girdle is stronger than the shoulder girdle and it supports your body while you are sitting or standing.

Arms and Forearms

Arms in your body start from the shoulder joint and end at the elbow joint, where the anterior half, forearm, starts and extends further outward. The terminal or posterior most part of your arm is known as hand, which is often listed as a separate skeletal entity. Excluding hand, both of your arms and forearms are collectively made up of as many as 6 bone units, namely, radius (2), ulna (2) and humerus (2). It will be just surprising to know that most of the physical activities you do in your routine life are accomplished by the hands, forearms, and arms.

Hands

Forming the posterior most part of your arms, hands are distinguished from other skeletal structures in the body from the presence of fingers and palms and contain as many as 54 bones in total. Out of these 54 bones, sixteen (16) are the carpals, ten (10) metacarpals, along with ten (10) proximal, eight (8) intermediate and ten (10) distal phalanges.

Thighs & Legs

Both thighs and legs, in combination, form one of the six structural and functional units of the appendicular skeleton in your body, where you will find 8 bones with the left and right pairs of fibula, tibia, patella and femur. The bony formations, found in the legs and thighs, are categorized among the strongest bones in the body as they can perform hectic tasks and are often used in vigorous activities.

Feet and Ankles

These form highly important parts of your appendicular skeleton, virtually remaining in contact with the ground and erecting you straight upward, thus forming an angle of 90o with the earth. The left and right feet and ankles are comprised of about 52 bones, out of which 14 are the tarsals while the remaining 38 are grouped in the separate categories of metatarsals, distal phalanges, intermediate phalanges and proximal phalanges.

HOW IT WORKS

The beautiful posture of your body and the versatility & complexity of functions you perform in your routine life are all owed to the existence and health of your skeletal system. Among a multitude of vital functions performed by the structural framework of your body, 6 are of primary importance. These include the essential accomplishments, like movement, support, protection, storage, blood corpuscle production and endocrine regulation. Let's have a bird eye view of these life-supporting functionalities, as described under:

Movement

You can have an idea about the supreme importance of movement that it is one of the major signs of the presence of life in an object, a thing or an entity. Here it is also worth noticing that if there were a single large bony structure in the body, the active and swift movement activities would have been almost impossible for you to perform. It is only primarily because of the firm and flexible joining of the 206 bones through which you can do all the dynamic tasks. Similarly, movement would not have been possible without the assistance and active participation of ligaments, muscles and tendons. All this is done via the formation of a large number of levers in the body, where the joints act as axis or fulcrum while the muscles crossing the joint serve as a source of force for the movement of a weight or resistance. The energy needed for the execution of these tasks is extracted from the food via metabolic processes.

Protection

The hard and firm bony framework in your body serves to protect many delicate and vital internal organs. For example, heart, lungs, liver, spleen and gall bladder are protected by the rib cage and the sternum. Likewise, the master organ brain is guarded by skull, which is one of the hardest bony structures in the body. You can have an idea about the protective potential of the skull that, regarding its hardness, it can be compared with the coconut shell, and there is needed a considerable force to break it apart. This is the very reason that in most of the horrible roadside accidents, many other bones get fractured but skull remains intact.

Support

The third most important function of the skeletal system is to provide support to all the structures of your body. It is owed to the functionality of your skeletal system that you can stand in erect form and maintain a beautiful body posture. The bones of the vertebral column, the pelvis and the legs work in mutual coordination to hold your body up. Teeth are supported by the mandible, while nearly all the bones provide direct or indirect support for all the soft organs and muscles.

Storage

The bones of our skeletal system also serve the purpose of the storage of fatty acids as well as certain essential minerals, which are utilized later on as needed by the body. Among the most notable mineral substances stored in the bones, there include calcium and phosphorus. In addition, bones also act as reserves for the storage of various growth factors; such as transforming growth factor; insulin-like growth factors; bone morphogenetic proteins; and so on.

Blood Formation

The bone marrow, found in the inner cavity of the bones, takes part in the formation of blood and the blood cells. At the same time, most cells of the immune system are also produced herein. In the process, called hematopoiesis, blood cells are produced in the marrow located within the medullary cavities of the long bones and the interstices of the cancellous bones.

Mineral Homeostasis

The maintenance of the perfect balance of different mineral substances is also one of the primary functions of the skeletal system. In this mechanism, excess quantities of minerals get stored in the bones and are released into the blood stream when needed for the accomplishment of vital activities in the body.

Acid-Base Balance

It has also been found that bones play a part in the regulation of optimum pH level of the blood. In order to buffer the blood against excessive pH changes, the bones either absorb or release the alkaline mineral substances into the blood stream. In this way, optimum acid-base balance is maintained for the successful completion of the vital enzymatic reactions taking place in the body.

Sound Transduction

The process of the conversion of the vibrational energy of the sound waves into electrical or neural energy is called sound transduction. The process of sound transduction is facilitated by the bones present in the ear. In addition, the bones also play an important role in the mechanical aspect of the overshadowed hearing.

Detoxification

The bone tissues are capable of removing certain heavy metals and other foreign elements from the blood and carrying out their detoxification. After reducing the effects of the harmful substances on the healthy body tissues, they are finally released for excretion.

Role in Endocrine System

Another important function of the bones is to control the metabolism of phosphate. For this purpose, FGF-23 (Fibroblas Growth Factor - 23) is released by the bones, which acts on the kidneys for the reduction of the phosphate reabsorption. Similarly, for the regulation of blood sugar and fat deposition, the bone cells release a hormone, called osteocalcin. Among the multiple functionalities of osteocalcin hormone, there include increase in the secretion of insulin and sensitivity; reduction of stored fat; and boost up in the number of insulin-producing cells.

INTERESTING FACTS

It is quite interesting to note that about 98 percent of all the animals inhabiting the planet earth do not have internal skeletons or backbones and are termed as invertebrates.
Only a minute percentage of the living animals have backbones or internal skeletons and are known as vertebrates, the more advanced of which are humans.
It is one of the most surprising human skeletal system facts that the bony structure of infants may be comprised of up to 350 bones.
The 300 to 350 bones found in human children during early developmental stages fuse together, thus reducing in number to just 206 till the age of nine.
Along with over two hundred bones, you can also find as many as 650 muscles attached to your skeletal system for the performance of versatile activities and the protection of internal organs.
Out of the 26 bones found in a human foot, 7 are grouped as tarsals, while the remaining nineteen fall under two different categories, namely, metatarsals and phalanges.
In each of your hands, there are 27 bones in total, which can be divided into carpals metacarpals and phalanges.
Three types of phalanges are found both in the hands and feet, which are proximal phalanges, distal phalanges and intermediate phalanges.
In the complex and mechanical structure of the feet, there are over hundred tendons, muscles and ligaments, and as many as 33 joints, out of which 20 are actively articulated as you walk or run.
There is no denying the fact that a single bony structure would not have allowed you all the briskness, variety and complexity of movements which you accomplish with the help of over two hundred bones, joined with one another through joints.
The real source of motility in the body is provided by the coordinated movements in muscles which, in turn, get energy from the food that you eat on daily basis.
Do you know that the teeth (composed of dentin and enamel) act as an integral part of the skeletal system but are not counted as bones?
The femur and the skull bones are much tougher to break, but even an average bone needs about 10 to 16 pounds of pressure to cause a fracture in it.
Talking of the structural composition of a bone, they are made up of cartilage, blood vessels, periosteum, bone marrow, spongy bone and compact bone.
The vertebral column, the skull and the rib cage are formed of 80 bones and, in turn, form the axial skeleton of your body.
Your appendicular skeleton contains a total of 126 bones which are used in various ways to form the pectoral girdles, the upper limbs, the lower limbs as well as the pelvic girdle.
The four specialized types of bones in your body are long bones, flat circular bones, long circular bones, and flat irregular bones.
Hips, skull and shoulder blades are strong but light flat irregular bones, that protect delicate organs, for example, brain.
Ribs are the strong and elastic long circular bones which render the chest flexibility and springiness which it needs to facilitate breathing.
Flat circular bones constitute the category of bones which are joined to form the spine or vertebral column.
Thin, hollow, light and long bones are found in limbs and play an essential role in all type of movements you make for the execution of miscellaneous routine life activities.
The largest bone in your body is the pelvis or the hip bone which is in fact made up of the six bones joined firmly.
With respect to location and structural differences, all the bones of spine or vertebral column can be grouped into five categories, namely, coccyx, sacrum, lumbar, thoracic and cervical vertebrae.
Out of the total 33 vertebrae of the human vertebral column, 24 are the articulating ones while the remaining 9 are fused vertebrae in the coccyx and the sacrum regions.
Situated in the dorsal aspect of the torso, your backbone contains a spinal canal to house and safeguard the spinal cord.
In the coccygeal or tailbone region, there are 4 fused vertebrae, while the sacrum is formed with the fusion of 5 such bones.
In the cervical, thoracic and lumbar regions of the backbone, you will find seven, twelve and five vertebrae, respectively.
Hyperkyphosis is an extreme case of the kyphosis or roundback disease which causes over 45o curvature in the thoracic region, thus resulting in very painful and ugly-looking physical deformity.