Engineering Terms (Electricity) Mr. McClean Concepts of Engineering

Electrons are the negatively charged particles of an atom Electrons are the negatively charged particles of an atom. Together, all of the electrons of an atom create a negative charge that balances the positive charge of the protons in the atomic nucleus. Electrons are extremely small compared to all of the other parts of the atom. The mass of an electron is almost 1,000 times smaller than the mass of a proton. It can be either free (not attached to any atom), or bound to the nucleus of an atom. Electrons in atoms exist in spherical shells, representing energy levels. The larger the spherical shell, the higher the energy in the electron. Electrons

The valence electrons are the electrons in the outer shell of an atom The valence electrons are the electrons in the outer shell of an atom. They are the ones involved in forming bonds to adjacent atoms. Therefore, the number of valence electrons is important for determining the number of bonds an atom will form. The valence electrons are the electrons on an atom that can be gained or lost in a chemical reaction. Valence Electrons

Protons are positively charged particles found within an atom Protons are positively charged particles found within an atom. A proton is a tiny particle, smaller than an atom. Protons are too small to see, even with an electron microscope, but we know they must be there because that's the only way we can explain how atoms behave. To give you an idea how small a proton is, if an atom was the size of a football stadium, then a proton would still be smaller than a marble. Protons

An atom is the smallest unit of matter that defines the chemical elements. Every solid, liquid, gas, and plasma is made up of atoms. Atoms are very small. Atoms are building blocks. If you want to create a language, you'll need an alphabet. If you want to build molecules, you will need atoms of different elements. Elements are the alphabet in the language of molecules. Each element is a little bit different from the rest. Atoms are the general term used to describe pieces of matter. You have billions of billions of atoms in your body. However, you may only find about 40 elements. Atoms

A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding. Covalent Bond

Voltage, also called electromotive force, is an expression of the potential difference in charge between two points in an electrical field. The greater the voltage, the greater the flow of electrical current. We define voltage as the amount of potential energy between two points on a circuit. One point has more charge than another. This difference in charge between the two points is called voltage. Voltage

The degree to which a specified material conducts electricity The degree to which a specified material conducts electricity. A conductor is an object or material that allows the flow of electricity, like a wire or piece of metal. Conductivity

An electrical insulator is a material whose internal electric charges do not flow freely, which makes it hard to conduct an electric current under the influence of electricity. An example is a rubber cord. A perfect insulator does not exist, because a portion of the insulator could become electrically conductive if the voltage applied across it exceeds the breakdown voltage. Insulation

In electronics, a circuit is a path between two or more points along which an electrical current can be carried. A circuit breaker is a device that interrupts the path when necessary to protect other devices attached to the circuit - for example, in case of a power surge. Circuit

A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Transistor

A power inverter is an electronic device or circuitry that changes direct current (DC) to alternating current (AC). An example would be a solar plant. inverter

A resistor is a passive two-terminal electrical component that implements electrical resistance. Resistors act to reduce current flow and act to lower voltage levels within circuits. In electronic circuits resistors are used to limit current flow, to adjust signal levels, terminate transmission lines among other uses. Resistor

An inductor, also called a coil, is a passive two-terminal electrical component which resists changes in electric currents passing. It consists of a conductor such as a wire, usually wound into a coil. When a current flows through it, energy is stored temporarily in a magnetic field in the coil. Inductor

A capacitor is a passive two-terminal electrical component used to store energy electrostatically in an electric field. All capacitors contain at least two electrical conductors (plates) separated by an insulating substance. Capacitor

In electronics, a diode is a two-terminal electronic component with asymmetric conductance; it has low (ideally zero) resistance to current in one direction, and high (ideally infinite) resistance in the other. Diode

An electrical device that can interrupt the flow of electrical current when it is overloaded. A fuse interrupts excessive current ("blows") so that further damage by overheating or fire is prevented. Fuse

A semiconductor is a substance that can conduct (allow) electricity under certain conditions but not others, making it a good medium for the control of electrical current. It is a solid substance that has a conductivity between that of an insulator and that of most metals, either due to the addition of an impurity or because of temperature effects. Devices made of semiconductors, notably silicon, are essential components of most electronic circuits. Semiconductor

A binary code represents text or computer processor instructions using the digits 0 and 1. A binary code assigns a bit string to each symbol or instruction. For example, a binary string of eight binary digits (bits) can represent any of 256 possible values and can therefore correspond to a variety of different symbols, letters or instructions. The number one represents the ON state or condition of a device. The number zero represents the OFF state or condition of a device. Combine billions of devices into one machine and you can wire them to do arithmetic calculations and sorting operations. Binary Code

Analog and Digital Signals Analog and digital signals are used to transmit information, usually through electric signals. In both these technologies, the information, such as any audio or video, is transformed into electric signals. The difference between analog and digital technologies is that in analog technology, information is translated into electric pulses of varying amplitude. In digital technology, translation of information is into binary format (0 or 1). Analog and Digital Signals

Alternating Current Direct Current Batteries, fuel cells and solar cells all produce something called Direct Current (DC). The (+) and (-) terminals of a battery are always positive and negative. Current always flows in the same direction between those two terminals. The power that comes from a power plant, on the other hand, is called Alternating Current (AC). The direction of the current reverses, or alternates. The power in a wall socket in the US is 120-volt of AC power. AC also has some useful properties, such as being able to convert voltage levels with a single device (a transformer), which is why AC was chosen as the primary means to transmit electricity over long distances. AC can be produced using a device called an alternator. Direct Current: Tank of Water Alternating Current Direct Current

A ground fault circuit interrupter (GFCI) is a device that shuts off an electric circuit when it detects that current is flowing along an unintended path, possibly through water or through a person. It is used to reduce the risk of electric shock. It works by measuring the current leaving the hot side of the power source and comparing it to the current returning to the neutral side. If they are not equal, this means that some of the current is flowing along an unintended path, and the GFCI shuts the power off. GFCI

When creating semiconductors, doping intentionally brings impurities into an extremely pure (Intrinsic) semiconductor for the purpose of changing its electrical properties. The impurities depend on the type of semiconductor. Lightly doped semiconductors are called Extrinsic. A semiconductor doped to such high levels that it acts more like a conductor than a semiconductor is referred to as Degenerate. Again, doping is the process of adding impurities to intrinsic semiconductors to alter their properties. N and P Doping

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