Fundamentals Of Electricity & Electronics

Fundamentals of ELECTRICITY & ELECTRONICS Fundamentals of Electricity What is Electricity? Electricity is a naturally occurring force that exists all around us. Humans have been aware of this force for many centuries. Ancient man believed that electricity was some form of magic because they did not understand it. Greek philosophers noticed that when a piece of amber was rubbed with cloth, it would attract pieces of straw. They recorded the first references to electrical effects, such as static electricity and lightning, over 2,500 years ago. It was not until 1600 that a man named Dr. William Gilbert coined the term “electrica,” a Latin word which describes the static charge that develops when certain materials are rubbed against amber. This is probably the source of the word “electricity." Electricity and magnetism are natural forces that are very closely related to one another. You will learn a little about magnetism in this section, but there is a whole section on magnetism if you want to learn more. In order to really understand electricity, we need to look closely at the very small components that compose all matter. Types of electricity There are two types of Electricity, Static Electricity and Current Electricity. Static Electricity is made by rubbing together two or more objects and making friction while Current electricity is the flow of electric charge across an electrical field. Static Electricity Static electricity is when electrical charges build up on the surface of a material. It is usually caused by rubbing materials together. The result of a build-up of static electricity is that objects may be attracted to each other or may even cause a spark to jump from one to the other. For Example rub a baloon on a wool and hold it up to the wall. Before rubbing, like all materials, the balloons and the wool sweater have a neutral charge. This is because they each have an equal number of positively charged subatomic particles (protons) and negatively charged subatomic particles (electrons). When you rub the balloon with the wool sweater, electrons are transferred from the wool to the rubber because of differences in the attraction of the two materials for electrons. The balloon becomes negatively charged because it gains electrons from the wool, and the wool becomes positively charged because it loses electrons. Current Electricity

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Current is the rate of flow of electrons. It is produced by moving electrons and it is measured in amperes. Unlike static electricity, current electricity must flow through a conductor, usually copper wire. Current with electricity is just like current when you think of a river. The river flows from one spot to another, and the speed it moves is the speed of the current. With electricity, current is a measure of the amount of energy transferred over a period of time. That energy is called a flow of electrons. One of the results of current is the heating of the conductor. When an electric stove heats up, it's because of the flow of current. There are different sources of current electricity including the chemical reactions taking place in a battery. The most common source is the generator. A simple generator produces electricity when a coil of copper turns inside a magnetic field. In a power plant, electromagnets spinning inside many coils of copper wire generate vast quantities of current electricity. There are two main kinds of electric current. Direct (DC) and Alternating (AC). It's easy to remember. Direct current is like the energy you get from a battery. Alternating current is like the plugs in the wall. The big difference between the two is that DC is a flow of energy while AC can turn on and off. AC reverses the direction of the electrons.

Chapter I: COMPOSITION OF MATTER Composition of Matter Elements All matter is composed of atoms. The number of electrons, protons and electrons determine the properties of those atoms. Matter is made up of elements. Elements are atoms with specific properties. The main property that defines each elements are the number of electrons, proton and neutrons. An example would be that of hydrogen and helium. Both of these are elements. The both have electrons, protons, and neutrons but the numbers of each are different. That difference alone allow for different chemical and physical properties. An element is defined as matter that is made up of the same kind of atoms. All sodium atoms have the same physical and chemical properties. All nickel elements have the same chemical and physical properties, although those properties those define each of the preceding elements are exclusive to those elements alone. There are 111 recognized elements and they are categorized according to their properties on the Periodic Table.

Compound

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A compound is composed of two or more elements of different kinds that are combined. The elements that make up a compound are always composed with the same elements in the same ratios every time. Glucose is always composed of 6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms. The properties of a compound are different that the elements from which it is made. Chemistry is defined as an organized body of knowledge concerning the composition of matter and how matter interacts and changes. Matter can be defined as anything that possesses the properties of mass and volume. Mass is the measure of a chunk of matter's ability to resist a change in movement or direction. The chemist calls this "inertia". Volume is the three dimensional space occupied by matter. It is a universal axiom that two chunks of matter can not occupy the same space simultaneously. All matter is composed of basic particles of atoms, molecules or ions. What are atoms? The basic of these particles are the atom. Atoms are particles that are composed of three sub-atomic particles. The three sub-atomic particles are the proton, neutron, and the electron. The proton is a positively charged particle that has the mass approximately equal to a hydrogen atom. It is said to have the mass of 1 atomic mass unit (amu). The protons reside in the nucleus or center of the atom. The neutron is a neutrally charged particle that is approximately the mass of a proton. The neutron does not have an electrical charge, but it also resides in the nucleus. The particles of the nucleus are called nucleons. The third particle of an atom is the electron. The electron is a negatively charged particle of negligible but finite mass. It resides on the outer edges of the atom with an enormous amount of space between the nucleus and the electrons. Because the protons and the neutrons are relatively well protected in the nucleus and the electron is on the periphery of the atom, it is the electrons that undergo change during a chemical reaction. It is the electrons that the chemist focuses upon. It takes millions of times more energy for the nucleus to be penetrated so the nucleus is not affected in normal chemical reactions. Atoms are neutral so that means that the positive protons and the negative electrons must be equal for the atom to be neutral. There are some 111 known different atoms that are differentiated by two numbers, atomic number and mass number. The atomic number is equal to the number of protons found in the nucleus. For a neutral atom that would also be the number of electrons in the atom. The mass number is defined as the sum of the protons and the neutrons in the nucleus of an atom. In other words, the mass number is the number of nucleons found in the atom. If I know the atomic number of an atom and the mass number then I can determine the number of electrons, protons, and neutrons that the atom has.

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What are molecules? Molecules are clusters of atoms that are held together by strong electrical forces called bonds. Molecules are neutral like atoms. Substances that form molecular units are called molecular substances. Just as elements can be symbolized by a symbol, molecules can be symbolized by the symbols of the elements that make up the compound. These are called formulas. Non-metallic elements react with other non-metallic elements to form molecular compounds

What are ions? Ions are the third basic particle of matter. Ions are charged atoms or groups of atoms possessing an electrical charge. Atoms are neutral possessing equal numbers of negative electrons and positive protons. However some atoms have a tendency to lose one or more negative electrons during a Chemical change. If the atom loses electrons that would mean that the atom would have more positive protons than negative electrons and the atom would become positively charged. These ions are called "cations". Metallic elements tend to lose electrons and become cations. Other atoms prefer to gain one or more negative electrons. This would give such an atom more negative electrons than protons and the atom would be negatively charged. These are referred to as "anions". Non-metallic elements have atoms that tend to gain electrons to become anions. Why do atoms lose or gain electrons? The whole motivation of why some atoms lose and some gain electrons is to make the atoms chemically more stable. They gladly sacrifice their electrical neutrality in favor of a more stable state. The more stable state is an ion that has the same number of electrons as one of the noble gases found in the last column of elements on the right of the periodic table. This condition is referred to as being "isoelectronic" to a Noble gas. These elements used to be called the "inert gases" because there were no known compounds of these elements. These elements are still relatively inert which a testament of their great stability is. All other elements have atoms that would like to emulate these noble gases. In other words, to be isoelectronic to a Noble Gas. The Noble gases were found to react with certain very chemically reactive elements like Fluorine and Oxygen and only Xenon has been known to form compounds of Fluorine and Oxygen. It is not surprising that such relatively stable elements would react with these two non-metals (Fluorine and Oxygen) If they were to react it would be the two most reactive non-metals in the universe. Why do elements lose or gain different numbers of electrons? All atoms would like to have the same number of electrons as a Noble gas because of their great stability. In order to accomplish that, some atoms must lose one and some more than one electron in order to have the same number of electrons as the nearest Noble Gas in the F.C. Ledesma Ave., San Carlos City, Negros Occidental Tel. #: (034) 312-6189 / (034) 729-4327

Periodic Table. For the first column of elements called Group 1 located in the first column on the left side of the Periodic Table each element in this Group have atoms that have only one electron that needs to be lost in order to reach this isoelectronic state with the nearest Noble Gas located on the last column on the extreme right of the Table called Group 18. The second column of elements in the Periodic Table called Group 2 has elements whose atoms have two electrons that must be lost to become isoelectronic to the nearest Noble Gas. On the other end of the Periodic Table, there are Groups of elements like Group 15 where atoms must gain three electrons in order to become isoelectronic to the nearest Noble Gas. Group 16 elements have atoms that must gain only two electrons to become isoelectronic to the nearest Noble Gas. Group 17 elements which are only one column to the left of the Noble Gas Group requires that its atoms need only to gain one electron. Basic Structure of Matter The Atom All matter such as solids, liquids, and gases, is composed of atoms. Atoms are almost always grouped together with other atoms to form what is called a molecule. Only a few gases such as helium are composed of individual atoms as the structural unit. Therefore, the molecule is considered to be the basic building block of matter. Atoms are extremely small. The radius of a typical atom is on the order of 0.00000000001 meter and cannot be studied without very powerful microscopes. In the next sub-units you will learn about what a material composed of only one type of atom is called and you will look at the basic model of an atom. Elements An Element defined Any material that is composed of only one type of atom is called a chemical element, a basic element, or just an element. Any material that is composed of more than one type of atom is called a compound. Every element has a unique atomic structure. Scientists know of only about 109 basic elements at this time. (this number has a habit of changing.) All matter is composed of combinations of one or more of these elements. Ninety-one of these basic elements occur naturally on or in the Earth. The other elements are man-made. You may recognize the names of some of these basic elements, such as: hydrogen helium, oxygen, iron, copper, gold, aluminum, uranium. The periodic table of elements (show below) lists the basic elements and some of their elements.

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ATOM MODELS What is an atom composed of? An atom is the smallest particle of any element that still retains the characteristics of that element. However, atoms consist of even smaller particles. Atoms consist of a central, dense nucleus that is surrounded by one or more lightweight negatively charged particles called electrons. The nucleus is made up of positively charged particles called protons and neutrons which are neutral. An atom is held together by forces of attraction between the electrons and the protons. The neutrons help to hold the protons together. Protons and neutrons are believed to be made up of even smaller particles called quarks. We will limit our discussions to protons, neutrons and electrons.

Niels Bohr was a Danish scientist who introduced the model of an atom in 1913. Bohr's model consists of a central nucleus surrounded by tiny particles called electrons that are orbiting the nucleus in a cloud. These electrons are spinning so fast around the nucleus of the atom that they would be just a blur if we could see particles that small. In our pictures and exercises the electron appears to orbit in the same path around the nucleus much like the planets orbit the Sun. But, please be aware that electrons do not really orbit in the same path. The electrons actually change their orbit with each revolution. F.C. Ledesma Ave., San Carlos City, Negros Occidental Tel. #: (034) 312-6189 / (034) 729-4327

ELECTRIC CHARGE Electrons Electrons are the smallest and lightest of the particles in an atom. Electrons are in constant motion as they circle around the nucleus of that atom. Electrons are said to have a negative charge, which means that they seem to be surrounded by a kind of invisible force field. This is called an electrostatic field.

Protons Protons are much larger and heavier than electrons. Protons have a positive electrical charge. This positively charged electrostatic field is exactly the same strength as the electrostatic field in an electron, but it is opposite in polarity. Notice the negative electron (pictured at the top left) and the positive proton (pictured at the right) have the same number of force field lines in each of the diagrams. In other words, the proton is exactly as positive as the electron is negative.

Like charges repel, unlike charges attract Two electrons will tend to repel each other because both have a negative electrical charge. Two protons will also tend to repel each other because they both have a positive charge. On the other hand, electrons and protons will be attracted to each other because of their unlike charges. Since the electron is much smaller and lighter than a proton, when they are attracted to each other due to their unlike charges, the electron usually does most of the moving. This is because the protons have more mass and are harder to get moving. Although electrons are very small, their negative electrical charges are still quite strong. Remember, the negative charge of an electron is the same as the positive electrical charge of the much larger in size proton. This way the atom stays electrically balanced. Another important fact about the electrical charges of protons and electrons is that the farther away they are from each other, the less force their electric fields have on each other. Similarly, the closer they are to each other, the more force they will experience from each other due to this invisible force field called an electric field. F.C. Ledesma Ave., San Carlos City, Negros Occidental Tel. #: (034) 312-6189 / (034) 729-4327

THE FREE ELECTRON Maintaining electrical balance Each basic element has a certain number of electrons and protons, which distinguishes each element from all other basic elements. In most elements, the number of electrons is equal to the number of protons. This maintains an electrical balance in the structure of atoms since protons and electrons have equal, but opposite electrostatic fields.

Pictured here is an atom of copper, which is much more complex than either an atom of hydrogen or helium. The copper atom has 29 protons in its nucleus with 29 electrons orbiting the nucleus. Notice that in the copper atom, the electrons are arranged in several layers called shells. This is to graphically represent that the electrons are at different orbits or energy levels within the atom. The energy of an electron is restricted to a few particular energy levels. The energy is said to be quantized, meaning that it cannot vary continuously over a range, but instead is limited to certain values. These energy levels or shells follow a very predictable pattern. The closest shell to the nucleus can have up to 2 electrons. The second shell from the nucleus can have up to 8 electrons. The third shell can have up to 18 electrons. The fourth shell can have up to 32 electrons, and so on. Atoms can have this many electrons, but they do not have to have this many electrons in each shell. The greater distance between the electrons in the outer shells and the protons in the nucleus mean the outer shell electrons experience less of a force of attraction to the nucleus than do the electron in the inner shells. In the next sub-unit you will learn about the the outer shell of an atom called the valence shell. THE VALENCE SHELL What is the valence shell?

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Notice that in the copper atom pictured below that the outside shell has only one electron. This represents that the copper atom has one electron that is near the outer portion of the atom. The outer shell of any atom is called the valence shell. When the valence electron in any atom gains sufficient energy from some outside force, it can break away from the parent atom and become what is called a free electron.

Pictured here is an atom of copper, which is much more complex than either an atom of hydrogen or helium. Atoms with few electrons in their valence shell tend to have more free electrons since these valence electrons are more loosely bound to the nucleus. In some materials like copper, the electrons are so loosely held by the atom and so close to the neighboring atoms that it is difficult to determine which electron belongs to which atom. Under these conditions, the valence or free electrons tend to drift randomly from one atom to its neighboring atoms. Under normal conditions the movement of the electrons is truly random, meaning they are moving in all directions by the same amount. However, if some outside force acts upon the material, this flow of electrons can be directed through materials and this flow is called electrical current. Materials that have free electrons and allow electrical current to flow easily are called conductors. Many materials do not have any free electrons. Because of this fact, they do not tend to share their electrons very easily and do not make good conductors of electrical currents. These materials are called insulators. There will be more information on this later.

Chapter II: SOURCES OF ELECTRICITY, CHARGES, AND STATIC ELECTRICITY Static Electricity Static electricity is an electric charge built up on persons or objects through friction. It is most familiar as an occasional annoyance in seasons of low humidity, but can be destructive and harmful in some situations. When working in direct contact with integrated

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circuits electronics, or in the presence of flammable gas, care must be taken to avoid accumulating and discharging static electricity. Static electricity is electricity that does not flow in a current. Static electricity is generated by rubbing two nonmagnetic objects together. The friction between the two objects generates attraction because the substance with an excess of electrons transfers them to the positively-charged substance. Usually, substances that don't conduct current electricity (insulators) are good at holding a charge. These substances may include rubber, plastic, glass or pitch. The electrons that are transferred are stored on the surface of an object. Materials Causing Charges Static electricity is created by putting certain materials together and then pulling them apart causes excess electrical charges to be created on their surfaces. This can be done by pushing them together and pulling them apart or by rubbing the materials together, which is the main way it is created. Excess Of Charges Most matter is electrically neutral. That means its atoms and molecules have the same number of electrons as protons. If a material somehow obtains extra electrons and attaches them to the atom's outer orbits or shells, that material has a negative ( - ) charge. Likewise, if a material loses electrons, it has an excess of positive (+) charges. The electric field from the excess of charges then causes the electric effects of attraction, repulsion or a spark (lightning).

Stealing Electrons According to Solar System Model (or Bohr Model) of the atom, electrons are in orbits or shells around the nucleus. A maximum number of electrons are allowed in each orbit. Forces in each atom seek to reach that maximum number, such that if an element is just one electron short of the maximum amount in its outer orbit, it would try to "steal" an electron from another element that may be just starting its outer orbit. This is the basis of chemical reactions. Adhesive Molecular Force That force will also tend to hold two different materials together. In that situation, the force is called the adhesive molecular force. When different materials are pressed together and then pulled apart, the adhesive molecular force pulls electrons from material unto the other. This creates the phenomenon. You can see this effect with a piece of Scotch tape or similar tape. First verify that it is not attracted to your finger. Then stick it to some surface and then pull it off. Put you finger F.C. Ledesma Ave., San Carlos City, Negros Occidental Tel. #: (034) 312-6189 / (034) 729-4327

near the tape and it will now be attracted to your finger, showing that there is an excess of charges on the tape. Despite their small size, protons and electrons carry an electrical charge. Protons carry a "positive" charge, while electrons carry a "negative" energy charge. Usually, the two different charges balance each other out, and nothing happens. But when two objects with like charges (all positive or all negative) come together, the charges repel and the objects move away from each other. Objects with opposite charges attract each other because the different charges want to enter a state of balance with each other. Objects can get a negative charge by picking up electrons from other objects. For example, when your shoes scuff against the rug, your shoes are actually picking up electrons from the rug. The electrons fly over your body, giving you a negative charge. Your new electrons fly over your body because they are looking for a positive charge. If you touch a metal doorknob, the electrons on your body will leap into the metal, attracted by the protons there. The transfer of electrons is actually a small electrical current, and produces the tiny electric shock you feel. Lightning is similar, except on a much bigger scale. Both lightning and static electricity happens because of the attraction between the opposite charges.

Not friction Although your can create it by pressing materials together and pulling them apart, rubbing them together works even better, except in the case of something sticky like tape. One unfortunate result from saying that rubbing materials creates this phenomenon is that most people think that friction causes the charges to build up. It is not friction that causes the spark, rather it is the adhesive forces that pull off electrons. Dry human skin and rabbit fur have the greatest tendency to give up electrons when rubbed on something and become positively ( + ) charged. Teflon and vinyl have the greatest tendency to become negatively charged ( - ) when rubbed. If you want to create a charge, rubbing fur on teflon should give the best results.

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