Category: Education
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4.8 Circuit fault analysis
Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose malfunctioning systems: determining in as short a time as possible the cause of a system’s malfunction. Since most instrumentation and control systems are based on electricity, a solid understanding of electrical faults is the foundation of this skill set.…
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4.7 Kirchhoff’s Laws
Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year 1847, known as Kirchhoff’s Laws. His two laws refer to voltages and currents in electric circuits, respectively. Kirchhoff’s Voltage Law states that the algebraic sum of all voltages in a closed loop is equal to zero. Another way to state…
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4.6 Series versus parallel circuits
In addition to Ohm’s Law, we have a set of rules describing how voltages, currents, and resistances relate in circuits comprised of multiple resistors. These rules fall neatly into two categories: series circuits and parallel circuits. The two circuit types are shown here, with squares representing any type of two-terminal electrical component: The defining characteristic of a series electrical…
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4.5 Electrical resistance and Ohm’s Law
To review, voltage is the measure of potential energy available to electric charges. Current is the uniform drifting of electric charges in response to a voltage. We can have a voltage without having a current, but we cannot have a current without first having a voltage to motivate it5 . Current without voltage would be equivalent to motion without a…
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4.4 Electrical power
Since we often use electricity to convey energy from one location to another, it is important to be able to quantify and calculate the rate at which energy is delivered by an electric circuit. The rate at which energy transfers from one location to another is technically referred to as power (P), and it is typically4 measured in the unit…
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4.3 Electrical sources and loads
By definition, a source is a device delivering energy into a system, while a load is a device extracting energy from a system. Examples of typical electrical sources include generators, photovoltaic cells, thermopiles, and primary-cell batteries. These devices create electrical voltage, which in turn motivates electrical current to flow in a circuit. Examples of typical electrical loads include resistors,…
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4.2 Electrical current
Current is the name we give to the motion of electric charges from a point of high potential to a point of low potential. All we need to form an electric current is a source of potential (voltage) and some electric charges that are free to move between the poles of that potential. For instance, if…
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4.1 Electrical voltage
Voltage is the amount of specific potential energy available between two points in an electric circuit. Potential energy is energy that is potentially available to do work. Looking at this from a classical physics perspective, potential energy is what we accumulate when we lift a weight above ground level, or when we compress a spring: In either case,…
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3.12 pH Explained
Hydrogen ion activity in aqueous (water-solvent) solutions is a very important parameter for a wide variety of industrial processes. A number of reactions important to chemical processing are inhibited or significantly slowed if the hydrogen ion activity of a solution lies outside a narrow range. Some additives used in water treatment processes (e.g. flocculants) will…
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3.10 Periodic table of the ions
3.11 Ions in liquid solutions Many liquid substances undergo a process whereby their constituent molecules split into positively and negatively charged ion pairs, the positively-charge ion called a cation and the negatively-charged ion called an anion37 . Liquid ionic compounds38 split into ions completely or nearly completely, while only a small percentage of the molecules in a liquid covalent compound39 split into ions. The process of…
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3.9 Energy in chemical reactions
A chemical reaction resulting in a net release of energy is called exothermic. Conversely, a chemical reaction requiring a net input of energy to occur is called endothermic. The relationship between chemical reactions and energy exchange corresponds to the breaking or making of chemical bonds. Atoms bonded together represent a lower state of total energy than those…
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3.8 Stoichiometry
Stoichiometry is the accounting of atoms before and after a chemical reaction. It is an expression of the Law of Mass Conservation, in that elements are neither created nor destroyed in a chemical reaction, and that mass is an intrinsic property of every element. Thus, the numbers, types of atoms, and total mass exiting a chemical reaction…
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3.7 Molecular quantities In Chemistry
Sample sizes of chemical substances are often measured in moles. One mole of a substance is defined as a sample having 6.022 × 1023 (Avogadro’s number) molecules25 . This number is not arbitrary – it was chosen26 such that 1 mole of carbon-12 (6.022 × 1023 individual 12C atoms together in one sample) would have a mass of exactly 12 grams. In other words, Avogadro’s…
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3.6 Formulae for common chemical compounds
Most of these formulae appear in molecular chemical form rather than structural form. For example, ethanol appears here as C2H6O rather than C2H5OH. Also, the entries for fructose and glucose are identical (C6H12O6) despite the two compounds having different structures. This means most of the formulae shown in this section merely represent the ratios of each element…
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3.5 Spectroscopy
Much of our knowledge about atomic structure comes from experimental data relating the interaction between light and atoms of the different elements. Light may be modeled as an electromagnetic wave, consisting of an oscillating electric field and an oscillating magnetic field. Like any wave, the relationship between propagation velocity, wavelength, and frequency is described by the following…