Electricity

What are molecules?

Combinations of atoms that make up the smallest part of a compound

Although it is known that atoms containing few valence electrons are the best conductors, it is not known why some of these materials conduct ______than others. Give example.

better/For example, aluminum, having 3 valence electrons will conduct electricity better than platinum, which contains only 1 valence electron.

When electrons hit each other during the flow of electricity, not all the ______ is transferred to the movement of each electron. Where does the rest go?

energy/ The rest is transferred into heat from friction of striking electrons.

What are conductors?

Materials that allow electrons to flow through them easily.

Producing electricity with heat is referred to as the ______effect.

seebeck

The production of electricity by pressure involves the _____________ of certain _______. This effect is referred to as the _____electric effect.

striking, bending, twisting/ crystals/ piezo

Semiconductors have been very important in the electrical industry since the invention of what?

the transistor in 1947

A static charge occurs when what happens?

when certain materials are rubbed together and electrons are transferred from object to the other.

The electron is about ____times larger than a proton.

3

The valence shell of an atom cannot hold more than ____electrons.

8

Describe the history of electricity from the beginning of the 18th century to the end of the 18th century.

In 1733, Charles Dufay's observations were published in a paper. He discovered that there were two types of electricity which he name "vitreous" and "resinous" (later known as positive and negative respectively). He noted the difference between conductors and insulators, calling them "electrics" and non-electrics" respectively. He also discovered that there were certain materials which when rubbed together would exhibit a force of repulsion. He also disproved certain misconceptions about electric charge, such as the notion that the electrical properties of an object was determined by its color. In 1752, Ben Franklin conducted his experiment with a kite, a key, and a storm and proved from the experiment that lightning and tiny little static sparks were the same thing. He established the connection between lightning and electricity. He also named like charges positive and unlike charges negative.

Describe the history of electricity from the beginning of the 19th century to the end of the 19th century.

In 1800, an Italian physicist Alessandro Volta invented the first battery he called the 'voltaic pile' after discovering that certain chemical reactions can produce electricity. The voltaic pile produced the first steady flow of electric charge, and so Volta was the first transmission and continuous flow of electrical charge. In 1831, Michael Faraday created the electric dynamo which was a crude power generator. This solved the problem of generating an electrical current in a practical and ongoing way. Faradays dynamo opened the door to American Thomas Edison and British scientist Joseph Swan who each invented the incandescent filament light bulb in their respective countries in about 1878. Previously, light had been invented, but the incandescent light bulb was an improvement and proved to light for hours on end. Later, Edison and Swan set up a joint company to produce the first practical light bulb and Edison used his DC system to provide power to illuminate the first New York electric street lamps in September 1882. Later in the 1800s and early 1900s, A Serbian American engineer, inventor, and electrical genius, Nikola Tesla became an important contributor to the birth of commercial electricity. He worked with Edison and later hand many revolutionary developments in electromagnetism, had competing patents with Marconi for the invention of the radio, and is well known for his work in AC. Later, American inventor and industrialist George Westinghouse purchased and developed Tesla's patented motor for generating AC, and the work of Westinghouse, Tesla and others gradually convinced American society that the future of electricity lay with AC rather than DC.

What is a photoemissive device?

Include photodiodes, phototransistors, photoscrs, etc. These devices are generally used to sense light when the speed of operation is imperative.

A conductor is made of a material that generally has ________ valence electrons. Insulators typically have ________valence electrons. Semiconductors contain ____ valence electrons.

1 to 3/7 or 8/4

Although the electron is larger than a proton, it is about _____times more heavier than a proton.

1,840

What are the six basic methods of producing electricity?

1. Magnetism 2. Chemical 3. Pressure 4. Heat 5. Friction 6. Light

What is a photoconductive device?

A device that changes its resistance with a change of light. The most common photoconductive device is the 'cad cell.' They exhibit a resistance of about 50 ohms in direct sun light and several hundred thousand ohms in darkness.

What is a photovoltaic device?

A device that produces electricity from the photons of light striking the valence electrons of its material out of orbit.

What is an element?

A substance that cannot be chemically divided into a simpler substance.

What is matter?

Any substance that has mass and occupies space.

Describe electron flow.

Electricity is the flow of electrons. It happens when an electron strikes another electron and knocks it out of orbit. The striking electron takes the place of the previous electron in the new electron orbit and the electron that got struck moves to strike another electron. A good analogy would be how a line of billiard balls hitting each other after being struck by one ball. When an atom contains very few valence electrons such as in a conductor, its valence electrons are very easily knocked out of orbit. When an atom contains many valence electrons, like in an insulator, the energy of a single electron striking 7 or 8 electrons is divided so many times that is has little effect on the atom.

Describe how electricity can be used to produce certain chemical reactions.

Electroplating. An object can be, for example, be coated with copper by placing a metal object to be coated and a piece of pure copper in a chemical solution. The object to be plated is connected to the negative electrode and the pure copper is connected to the positive electrode. Electrolysis is another example. Electrolysis is the process of chemically separating elements.

Just as applying pressure to certain crystals can cause electricity, electricity can cause the bending and twisting of certain crystals. Give example.

For example, when electricity is applied to a certain size and shape of quartz crystal it will vibrate at a certain rate. This principle has been used in crystal radios for many years. If an electric current is applied to a piece of Rochelle salt crystal, the crystal will vibrate. This is the principle of a crystal earphone.

Describe how electricity is produced from light.

It involves the use of particles called 'photons'. In theory, photons are massless particles of pure energy. Photons are produced when electrons are forced to change energy levels, or are knocked out of orbit. This is the operating principle of gas-filled lights such as sodium vapor, mercury vapor, etc. Incandescent lamps also use this principle. When an electric current is applied to the filament of an incandescent lamp, most of the electrical energy is converted into heat, but part produces photons of light. The typical 100 watt bulb produces about 95 watts of heat and 5 watts of light. sodium vapor and mercury vapor are much more efficient. Some semiconductor devices can be used to produce light without heat such as light emitting diodes.

Before any pure semiconductor can be used to construct an electronic device, what must be done to it?

It must be mixed or "doped" with an impurity.

What are semiconductors?

Materials that are neither good conductors nor good insulators. They are also characterized by the fact that as they are heated, their resistance decreases. Heat has the opposite effect on conductors as they are heated-their resistance increases.

What are insulators?

Materials that resist the flow of electrons.

Describe the history of electricity after the Greeks discovered it to the end of the 17th century.

Researchers and archeologists in the 1930's discovered pots with sheets of copper inside that they believe may have been ancient batteries meant to produce light at ancient Roman sites. Similar devices were found in archeological digs near Baghdad meaning ancient Persians may have also used an early form of batteries. Aside these archeological finds, the attractive force of amber remained nothing more than a curious phenomenon until about 2,000 years later from when the Greeks discovered static electricity when other people began to conduct experiments with it. In the early 1600s, English physician William Gilbert discovered that amber was not the only material that could be charged to attract other objects. He used the term 'electricus' to describe the forces that these materials exhibited on each other. He also invented the first electrical measuring instrument-the electroscope-which measured electric charge. Thomas Browne, wrote several books and he used the word "electricity" in one of his writings in 1646 to describe his investigations based on Gilbert's work.

What are the two most common materials used in the production of semiconductors?

Silicon and germanium. Silicon is used most often because of its ability to withstand heat.

______is the best natural conductor followed by ________

Silver/copper, gold, and aluminum

How was electricity discovered?

The Greeks were the first to discover it about 2500 years ago (600 bc). They noticed that when they rubbed amber with other materials, such as dried leaves, feathers, and bits of cloth, it became charged with an unknown force of attraction between the two. The Greeks called amber 'electron'. The word 'electric' was derived from it and meant "to be like amber", or have the ability to attract other objects. So the Greeks actually discovered static electricity.

The number of protons in an atoms nucleus determines what?

The element that it is.

What are two theories explaining why protons don't repel each other in the nucleus.

The first asserts that the combined force of gravity of the neutrons in the nucleus prevent the protons from repelling away from each other. The second asserts that there is a theoretical subatomic particle called a 'gluon' that acts as a bonding agent and that not only holds protons and neutrons together, but also holds quarks together.

Describe the lines of force of positive and negative charges.

The lines of force extend outward from a positive charge while the lines of force extend inward into a negative charge.

What is the 'atomic number' of an atom?

The same as the number of protons in the nucleus.

What is an atom?

The smallest part of an element.

The chemical production of electricity involves the movement of entire _________instead of just electrons.

ions

There are limitations to the number of electrons that can be in certain electron ____________. Explain.

orbits/The first orbit can hold no more than 2 electrons. The second orbit, no more than 8 electrons. The third orbit, no more than 18 electrons. The fourth and fifth orbits cannot hold more than 32 electrons. 32 is the maximum number of electrons than can be contained in any orbit.