This month in The Classroom, we&#;ll take a break from absolute theory and instead look at something students and makers alike need to understand: identifying and correctly using some basic electronic components.

Are you interested in learning more about wholesale power resistor supplier? Contact us today to secure an expert consultation!

One of the most common components any maker or student encounters will be resistors. Resistors come in a huge array of types and sizes, values, and power ratings.

In an average classroom kit or programmer&#;s board like Arduino or Raspberry Pi, the most commonly found components are the small signal resistors in the 0.25W-0.5W range.

What are resistors, and what does the other jargon (&#;metalanguage&#; for all the educators out there), actually mean?

Resistors are components designed to resist the flow of electricity, thereby reducing current flow, limiting voltage, or generating heat, often very precisely. Resistors are literally meant to get in the way, but only a little bit. The measurement of that resistance (i.e. the &#;value&#; of a resistor) is given in Ohms, which is symbolised using Ω. In Australia, the circuit symbol for a resistor is a rectangle with the value next to it or in it, always given in Ohms. Previously, the symbol for a resistor was a zig-zag line. You will often still find it in current literature too.

Fixed Range of Values

Resistors are typically made in set values. You may have heard of the E12 series or the like. This means that for each power of 10, there are 12 values of resistor. So from the range 10Ω to 100Ω, there will be 12 values: 10Ω, 12Ω, 15Ω, 18Ω, 22Ω, 27Ω, 33Ω, 39Ω, 47Ω, 56Ω, 68Ω, 82Ω. For the next power of 10 &#; being 100Ω to Ω &#; there will be another 10 values, basically the same numbers but ten times greater.

This is the system engineers developed so the percentage gap between values remains the same. E12 are for 20%, E24 for 10%, E48 for 5% and so on. The E series is defined by internationally standards, and not just for resistors.

However, some resistors, called &#;High Precision&#;, are made to a specific value for a specific use. In the world of RF, 50 Ohm resistors may be required. So, although most resistors conform to the E12, E24 or other series, occasionally you might find something different. It is unlikely to buy anything other than E24 values at an electronics shop.

The Power

When you&#;re looking at a parts list, the next number you&#;ll typically see in a resistor name is a power value in watts. In real terms, this means the amount of power that a resistor can turn into heat before becoming physically damaged. Many of the resistors in educational kits, experimenter&#;s kits, and on Arduino and Raspberry Pi boards are 0.25W or 0.5W sized. You may have 1/8th Watt, (0.125W) in very small or even SMD resistors, but again won&#;t usually buy them for a project.

Interestingly, even though 0.5W dissipate twice the heat of the 0.25W, they are both the same size due to how they are made. 0.25W resistors are usually carbon film types. That is, they are a film of carbon around a ceramic former, with a metal cup and leg attached at each end. The resistor is covered in a protective coating of a colour that reflects the technology used. The coating carries information about the resistor via colour coded bands.

In contrast, 0.5W resistors are usually made with a metal film on the ceramic core, which can handle more heat for its size than carbon film. Metal film resistors are the most common today, after carbon film.

There are other sizes, and types of resistors around. Resistors rated at 1W or even 2W look a lot like a larger version of a 0.5W type, but can dissipate more heat. The 5W, 10W and 20W resistors, as found at your electronics store, are of a construction called wire wound, ceramic case. These are &#;Power Resistors&#; made with fine wire that is wound around a ceramic former, coated in ceramic compound, and embedded in a rectangular ceramic carrier, which both protects the resistance and dissipates heat.

Larger resistors are available, but they are usually hard to find and well out of the needs range of most of us. In fact, the elements in a Stove Hotplate or Electric Heater, Electric Hot Water System, or even an Electric Blanket, are resistors.

Tolerance

The next parameter you will find in a resistor&#;s description is its tolerance. This is not always stated, but it is sometimes important, especially to the designer.

Whenever an engineer designs a part, as well as other dimensions, that part will have the tolerances specified. In many industries, this will be a range of acceptable sizes or other dimensions. Typically parts will be given a &#;Nominal&#; value, perhaps in metres or millimetres, and a &#;Tolerance&#; in millimetres or even micrometres.

For example in an Aluminium extrusion factory I used to work in, Aluminium tubes were cut to 3.6m +/- 2mm. I had to ensure that each each tube was between mm and mm.

Although resistors have physical dimensions and tolerances, the important tolerance is of the actual resistance. Unavoidable differences exist in any batch of material, so although a precisely calculated and applied layer of metal film is deposited on the ceramic, and then laser cut, or trimmed, the exact resistance will be between the two values of tolerance, the upper tolerance, and the lower tolerance.

Electronic component manufacturers work in percentages for their tolerances. Commonly, metal film resistors have a tolerance of +/- 1%, while carbon film resistors often have a value of +/- 5%.

This means that a given metal film resistor may be lower or higher than its stated value, by an amount of up to one per cent of that value. In real terms, a 100Ω resistor may be up to 1%, or 1Ω, higher or lower, making it potentially anywhere between 99Ω and 101Ω.

Tolerance values are written on resistors with a tolerance of better than 20%, as the fourth or fifth band on a resistor, depending on the type. Colour banding is discussed below. Some applications allow a wide range of tolerances without a significant issue, but others require a high level of accuracy, i.e. a low tolerance for error. Electronic Instrumentation for example becomes less accurate with badly chosen values of resistance.

Knowing Versus Finding

The resistance, power rating, and tolerance of a resistor are certainly the three main pieces of information needed for most of us to choose and use a resistor. Although not discussed here, some resistors also show a temperature band, although not normally required for hobbyists.

So, how does one find this information on the actual resistor? In the case of power dissipation, this is basically indicated by size, but the background colour defines the type of technology in the resistor. Carbon Compound Resistors had a brown body, but were rated at several power levels and poor tolerances. Carbon Film have a cream body and also come in different power levels, Metal Film are often blue, and so on.

Knowing the technology therefore helps find the power dissipation levels, but, if you are purchasing new components, then that information will be included in the packaging or the catalogue, or the manufacturers data sheet. Often, a project or kit comes with metal film resistors, and when one is lost or damaged in assembly, a common mistake is to replace it with the same value carbon film type. Remember carbon film (cream) are half the power rating of Metal Film (blue).

Resistors of 5W and above actually have the dissipation stamped on them, although size is a fair guide too. You will quickly come to recognise what is normally a 5W, 10W or 20W Ceramic Block Wire Wound Resistor.

There are three common systems that manufacturers use to detail the value and tolerance information for resistors. As stated above, at the 5W mark and above, resistors are large enough and made of a suitable material and shape to have the information stamped or printed on them. The value may be written as a number, such as 100Ω, but this is less common. Instead, a decimal multiplier system is usually used. Two are common: the first is the same decimal system we are familiar with from weight, volume, and mass measurement. That is, below , resistance is simply printed straight on the resistor with the letter &#;R&#; after it. This is because the symbol for Ω often looks far too similar to a &#;0&#;.

For numbers between 1,000Ω and 1,000,000Ω, the decimal multiplier &#;K&#; is used. This is also often abbreviated in speech as just &#;K&#;, for Kilo-ohms, which is often called &#;Kilohms&#; with a single &#;Oh&#; sound. Grammar fanatics like the primary teacher in me struggle with this, but as it is a piece of jargon or metalanguage, absolute grammar rules do not apply.

For numbers one million Ohms or more, the letter &#;M&#; is used, for &#;Mega-ohm&#;, which is often pronounced &#;megohm&#; and simply abbreviated to &#;Meg&#;. For many of us, these letters are familiar from day-to-day life, being standard Metric terms.

As an exercise, teachers should collect a number of 5W to 20W resistors, or find some in an old TV or such, and compare the markings. Decimal points get easily lost or confused with dirt and stray marks. For this reason, a value of, say, 4.7Ω will often be stamped as 4R7. Likewise, will be stamped as 4K7. Including the multiplier as the decimal point creates clarity and removes doubt, and reduces the number of characters to be printed, but can confuse new users.

Tolerance is stamped with a single letter code, and unfortunately, while there are industry standards, in my experience, manufacturers may apply their own rules.

Generally, you will find they are labelled &#;K&#; for 10%, &#;J&#; for 5%, &#;G&#; for 2% and &#;F&#; for 1%. There is a problem here though, as K is used as both the decimal multiplier, and the common tolerance of 10%. So care is needed here, although thankfully, the tolerance letter is usually all by itself, away from other letters and numbers, and nearer the edge of the component.

Two of Three

The second textual system is also used on larger format resistors, and usually on surface mount devices. This system consists of three numbers and a letter. The letter is the same tolerance indicator as above, making that one fairly easy, as long as you do not mistake the &#;K&#; for kilohms.

The three numbers are not as complicated as they look. What you are looking at is two significant figures and an exponential number, or multiplier. Think of it as a simplified scientific number. The multiplier is literally the number of zeros that follow after the two significant figures.

For example, a marking of &#;152&#; is the same as Ohms, where 1 and 5 are the significant figures, which are 2 place values (or 2 zero's) away from the decimal point. Likewise, 473 is actually 47,000Ω or 47kΩ. In all cases, the number will be in ohms when expanded with all the zeros. There are some challenges with this system for smaller values. In fact, I have only seen it used recently on variable resistors, but more about these soon.

It&#;s All About The Colour

So this is all well and good for the larger resistors, which are big enough to physically print numbers on, and for SMDs that use very good printing, but what about the simple resistors that most of us use? Although some readers may measure every resistor on their multi-meter, most readers will be familiar with the little coloured bands seen on these resistors, and some can read them.

These coloured bands painted around the case may look random, but there is a reason to them, and a formula to read them. What you should have is a total of four or five bands, (occasionally six) with one being separated from the others by a larger gap. This is not always the case however, so be careful! If all is going according to plan and you do have three or four bands, then a gap, then one more, well your life is easier! Read it from one end, and if it doesn&#;t make sense, and doesn&#;t appear to be a standard value, try reading it from the other end.

The numbers grouped together are either two or three significant figures, then a multiplier, and each coloured band represents a number [1].

1

The first two in a three-band group indicate the value, and the third is the number of decimal places. In a four-band group, you have three significant figures and one multiplier. The multiplier works out to literally be the number of zeros you add after you figure out the significant figures as in our second method above.

The band all on its own indicates tolerance, which is also identified by its colour, which can be helpful if the spacing isn&#;t great.

So for a five-band resistor with colour coded bands of brown, green, black, red and brown, has significant figure values of 1, 5, and 0, and a multiplier of 2. There is also a tolerance band representing 1%. Therefore, the resistor will be 1, 5, 0, and two 0s, equating to 15 000Ω 1% or 15k 1%.

A four-band resistor will only be 5% tolerance at best. So the same value, 15k will be 1,5,3, will have bands of brown green, orange, gold. There may not be a gap before the tolerance band, but as the tolerance will only be 5% (gold) or 10% (silver) they will be easily recognised as the tolerance band.

Values of resistor below 10 Ohms are uncommon but still required to be marked. For example a 1.2 Ohm resistor is 12 with a multiplier of 1/10. The appropriate multiplier code for that is a gold band. Similarly a 1/100 multiplier is represented by a silver band.

Colour banding is the most common type of resistor marking that most of us will come across.

Changing Resistance

There is a lot of information here; but wait, there&#;s more! It&#;s also worth discussing a different type of resistor: the variable resistor.

Many circuits use adjustable resistors, or variable resistors, to control volume, speed, brightness, and on/off thresholds. Variable resistors are typically rotary types that revolve about 270 degrees, but some are sliding types as used on Audio mixing desks. Yet others are multiple turn rotary or screw types. As with fixed resistors, the common variable resistors are only able to dissipate a little heat, so they are often used to control a driving circuit.

In their most common form, variable resistors feature a carbon film deposited on a resin bonded paper base, which is held in a pressed steel frame, with a rotor shaft through the middle of a mounting boss. The rotor is connected to a wiper, which touches and slides along the carbon film. The ends of the film are connected to the outer pins of the case, while the wiper is connected to a third contact.

Current flows in one pin into the carbon track and out the wiper. At the initial position there will be very little resistance and possibly a direct contact with the pin, but as the wiper begins to move around the carbon track, current must flow through more and more carbon in order to reach the wiper. At around 270° of travel, the wiper reaches the other end of the track. The current must pass through almost all of the carbon in order to reach the wiper. In this way, the resistance between the wiper [2] and the pin at the other end varies from ~zero to the nominal resistance of the track.

2

There are variations on this theme. Some variable resistors slide like the volume control faders on a sound desk in a music space. Others are built for operation through 90°, such as those in radio control situations. Still others look like the regular 270° round variable resistors but are wire-wound for increased power handling.

Yet another variation is the trimpot. These are smaller variable resistors, which are adjusted by a screwdriver or dedicated tool. They are used for &#;set and forget&#; applications, like adjusting upper and lower limits of a larger range. Trimpots come in a variety of forms from open frames with carbon film to 25-turn precision wire-wound varieties.

What&#;s in a Name?

Many people think a variable resistor is called a &#;potentiometer&#; but this is not strictly true as the term potentiometer actually refers to a voltage divider. Originally the Potentiometer was a piece of Science Lab equipment to measure voltage in an experiment. A voltage is applied to one end, current flows through the whole resistance and exits somewhere into the circuit at the other end. The variable wiper taps off the desired level of that signal, as a part voltage of the total, for the circuit to use [3]. It is the application of a variable resistor that determines its name; however, as most often we are connecting them as potentiometers (or &#;pots&#; for short), most of us know them by this name.

3

A variable resistor may also be used as a rheostat. In the rheostat, a voltage is applied at one end, but the other end is either not connected, or connected to the wiper. The resistance itself is the variable value, causing variation in the current passing through it, or the voltage across the rheostat.

In the case of a potentiometer, having three terminals means that the current entering one terminal is divided between the other two terminals. The voltage on the wiper is always a value between the values at either end pin. Most designs are calculated to have a current passing through the carbon track, that is ten to twenty times the current at the wiper terminal, so the wiper current makes a negligible difference to the voltage at the wiper position.

The circuit symbols for some variable resistors are shown here too. You&#;ll see that the chief difference is the screw-adjust type versus the fully variable, hand-adjusted type.

What Does It All Mean?

Now that you can identify most resistors in both physical form and circuit diagrams, it&#;s time to learn a bit about how to use them. As alluded to in the beginning of the article, resistors exist to oppose the flow of electricity. Those who have read previous editions may remember resistance as being like a smaller section of pipe that slows water down; resistors are basically just that. You might want to do this for timing reasons, or to reduce the current flowing through a component to a safe level.

All resistors follow Ohm&#;s Law, which states that the voltage being dropped across the resistor (the potential difference existing across it) is equal to the resistance of the component (in ohms) multiplied by the current flowing through it (in amps). It is important to convert milliamps (mA) to amps (A) before doing this though, as many people struggle otherwise.

"In any given circuit, where the voltage remains constant, the current in such a circuit is directly proportional to the resistance of that circuit."

The easiest way to remember the formula is to draw it as a triangle [4] with V at the "Very top", and R on the "Right". That leaves only one place for I, which is the letter we use to represent current.

4

As a practical example, let&#;s take the common LED. LEDs are made to emit light (we will cover PN junctions, diodes, and LEDs in future editions), and as such, they are not manufactured to be rugged. So an LED that draws 30mA at 2.3V voltage drop would quickly burn out if connected to 5V. In fact, as an LED has no current limiting properties, it would burn out even if running on 2.3V with no resistor.

For this reason, we need a resistance in series with the LED as a current limiter. This resistance is correctly called a &#;Ballast Resistor&#;. To calculate the ballast resistor value, we need to use Ohm&#;s Law. If the supply is taken as 5V, and the LED terminal voltage when lit is specified as 2.3V, the voltage difference across the resister needs to be 5 &#; 2.3 = 2.7V. The specified LED current is given as 30mA, which is 0.03A. Remember: We must always work in amps, volts, and ohms, never their multiplied or divided versions such as &#;milli&#;.

Using Ohm&#;s Law to calculate the resistance or our resistor, we have a voltage drop (desired) of 2.7V (V at the Very top of the triangle), and the current (I - below left) 0.03A, i.e. underneath the 1.8V, which looks like this:

2.7 / 0.03 = 90 - This gives a result of 90Ω. The nearest standard E12 value is going to be 82Ω or 100Ω, which are both about the same percentage difference, so we would normally use the higher value and accept a little lower light output.

Let&#;s try again for the same LED, but running this time on a 12V supply. Now we need to drop (12V - 2.3V = 9.7V) at the same 0.03A.

9.7 / 0.03 = 323.3 - In this case, the resistance is calculated as 323.3, which is again a non-standard value; so to run our 2.3V, 30mA LED on 12V, go to the next higher standard value of resistor, which would be 330R.

There are many other reasons for using a resistor, although unfortunately many are far beyond the scope of this article. Most are very situational, such as timer circuits where the resistor controls the charge rate of a capacitor to reach a threshold voltage to set a flip-flop; however, that is worthy of a whole other article!

Hopefully you have the knowledge now to identify the type, tolerance, and value of the resistors you are working with, and a basic understanding of how to safely use LEDs in your circuits. Remember, the DIYODE classroom only exists as long as you continue to let us know what you want to learn about, so please keep those topic suggestions coming in.

This glossary encompasses terms used in the electric energy industry and includes additional industry terminology.

Aggregator: An entity that puts together groups of customers into a buying group that purchases a commodity service. Many communities are engaged in municipal aggregation programs for electric and natural gas.

American Municipal Power (AMP): Nonprofit organization based in Columbus, Ohio and providing wholesale power supply and services to 108 member municipal electric communities in Ohio, Michigan, Pennsylvania and West Virginia.

Ampere: The standard unit of measuring the strength of an electric current.

Ancillary Services: Services or tariff provisions related to provision of electricity, other than simple generation, transmission or distribution. Ancillary services related to transmission service include: energy losses, energy imbalances, scheduling and dispatching, load following, system protections and reactive power. Ancillary services related to distribution include meter reading, billing and collections.

Auction Revenue Right (ARR): In some energy market systems, financial transmission rights are obtained through an auction. Revenue gained through this auction is paid to ARR holders. Transmission customers may receive ARRs for purchasing firm transmission service.

Available Transfer Capability (ATC): The amount of electric power that can be transferred over the interconnected transmission systems in a reliable manner under base case conditions.

Base-Load Generation: Facilities designed to run constantly at near capacity levels, to meet basic demand.

Bulk Power Supply: Often used interchangeably with wholesale power supply. In broader terms, it refers to the aggregate of electric generating plants, transmission lines and related equipment. The term may refer to those facilities within one electric utility, or within a group of utilities in which the transmission lines are interconnected.

Capacity Benefit Margin (CBM): The amount of inter-utility transmission transfer capability held in reserve to help ensure that there is a reliable source of power even if the utility experiences problems with its internal generation.

Certified Territory: An area established by the Public Utilities Commission of Ohio that determines the distribution customers an investor-owned or rural electric cooperative will serve.

CO2: Carbon dioxide

Contract Path: A specific contiguous electrical path from a Point of Receipt to a Point of Delivery for which transfer rights have been contracted.

Co-op: Commonly used term for rural electric cooperative. Rural electric cooperatives generate and purchase wholesale power, arrange transmission of that power and then distribute the power to serve the demands of rural customers.

Demand-Side Management: Methods used by end-users to manage their energy usage. Methods may include energy efficiency efforts, load management, fuel substitution and load building. AMP-Ohio offers a load management program that can assist with feasibility studies, engineering, implementation and operation.

The company is the world’s best types of fixed resistors custom supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

Deregulation: The elimination of regulation from a previously regulated industry or sector of an industry.

Distributed Generation: A system involving small amounts of generation located on a utility's distribution system for the purpose of meeting local peak loads.

Distribution Company (Disco): The regulated electric utility that constructs and maintains distribution wires connection the transmission grid to the final customer. The Disco can also perform services such as aggregating customers, purchasing power supply and transmission service for customers, billing customers and reimbursing suppliers and offering regulated or nonregulated services to retail customers.

Divestiture: The separation of one utility function from another by selling, spinning-off, or in some other way changing the ownership of the assets related to that function. Most commonly associated with spinning-off generation assets so they are no longer owned by the shareholders who own the transmission and distribution assets.

Epact: The Energy Policy Act of addresses a wide range of energy issues. The legislation created a new class of power generators, exempt wholesale generators, that are exempt from the provisions of the Public Utilities Holding Company Act of and grants authority to FERC to order and condition access by any party to the interconnected transmission grid.

Federal Energy Regulatory Commission (FERC): An independent agency within the Department of Energy that regulates the transmission and wholesale sales of electricity in interstate commerce; licenses and inspects private, municipal and state hydroelectric projects; oversees environmental matters related to natural gas, oil, electricity and hydroelectric projects; and administers accounting and financial reporting regulations and conduct of jurisdictional companies.

Fiber Optic: Thin transparent fibers of glass or plastic that transmit light through their length by internal reflections, used for transmitting data, voice, and images. Fiber-optic technology has virtually replaced copper wire in long distance lines and is used to link computers in local area networks, with digitized light pulses replacing the electric current formerly used for the signal.

Financial Transmission Rights (FTR): A financial instrument used in locational marginal pricing (LMP) energy markets to hedge the cost of congestion between the point of receipt and the delivery of a power supply contract.

Fine Particulate Matter: An atmospheric pollutant linked to emissions from a variety of sources; once emitted, the material is subject to transport and transformation in the atmosphere. Fine particulate matter is characterized as being less than 2.5 microns in aerodynamic diameter.

Futures Market: Arrangement through a contract for the delivery of a commodity at a time and price specified at the time of purchase. The price is based on an auction of market basis.

Generation Company (Genco): A regulated or nonregulated entity (depending upon the industry structure) that operates and maintains generating plants. The Genco may own the generation plants or interact with the short-term market on behalf of plant owners. In the context of market restructuring for electricity, the term is used most often to describe a specialized "marketer" for generating plants formerly owned by a vertically integrated utility.

Ground-Level Ozone: A high accumulation of ozone gas in the lower atmosphere at ground level is air pollution and can be harmful to people, animals, crops, and other materials.

Hedging Contract: A contract to establish the sale of futures against the purchase of electric power to protect against a decline in value; conversely, the purchase of futures against forward sales of, or anticipated need for, power to protect against an increase in value.

Home Rule: A provision of the Ohio Constitution preserving the authority of local decision-makers to determine the economic and social impact of policy changes regarding municipalities in the state.

Independent Power Producer (IPP): An independent company, owned by investors, that generates electricity and is not regulated by FERC.

Independent System Operator (ISO): A company or organization that would act independently of its parent companies or organizations to operate the power transmission grid for a specified geographic area. Owners retain their assets and the ISO runs the system as a joint operation. The ISO files a single transmission tariff for the region, plans and schedules transmission outages, takes a lead role in transmission system planning, collects transmission charges and makes payments to providers.

Independent Transmission Company (ITC): An independent, for-profit entity with management responsibility for transmission assets.

Independent Transmission Provider (ITP): Defined by FERC as any public utility that owns, controls or operates facilities used for the transmission of electricity in interstate commerce, that administers the day-ahead and real-time energy and ancillary services markets in connection with its provision of transmission service and has no financial interest, either directly or through an affiliate, in any market participant in the region in which it provides transmission service or in neighboring regions.

Integrated Resource Planning (IRP): A public planning process and framework within which costs and benefits of both demand-and supply-side resources are evaluated to develop the least-total cost (social cost) mix of utility resource options. The IRP has become a formal process set by law in some states and under some provisions of the Clean Air Act Amendments of .

Interconnection: The physical plant and equipment, usually at transmission-level voltage, that transfers electric energy between two or more entities. It can consist of a substation and an associated transmission line and communications facilities, or a simple electric power line or switching station.

Interconnection Agreement: An agreement between two interconnected utilities that provides for mutual services across interconnections, such as short-term power sales and purchases, emergency power sales and purchases, and third-party power sales and purchases.

Investor-Owned Utility (IOU): Private, for-profit utility company

Kilovolt (kV): 1,000 volts

Kilowatt (kW): 1,000 watts

Kilowatt Hour (kWh): The amount of electricity needed to light 10, 100-watt light bulbs for a one-hour period. One thousand watts used for one hour.

"License Plate" Rate: Created to eliminate "pancaking" of rates (adding one rate on top of another), this method allocates the cost of transmission facilities to local load, and provide access to a regional transmission system at a single rate, although the rate may vary based on where a customer is located.

Load Management: See Demand-Side Management.

Locational Marginal Pricing (LMP): The market clearing price for electrical energy at the location the energy is delivered or received from the transmission system. The price is the cost of supplying the next increment of load, taking into account the physical limitations of the transmission system.

Mark-to-Market (MtM): An accounting method that describes how a trader calculates its trading gains and losses (the amount calculated) and how these gains and losses are reported on a traders annual income tax returns.

Market Power: (a) The ability of a seller to charge rates in excess of costs for a significant period of time because competition is limited by some impediment; (b) Power available for sale at the market price in an unregulated mode.

Marketer: An agent that markets power for the generator. The marketer may arrange transmission or other ancillary services as needed.

Maximum Achievable Control Technology (MACT): The Clean Air Act Amendments for the control of hazardous air pollutants established a new and fairly complex program for the control of hazardous air pollutants through the application of this control technology. Congress required the EPA to regulate 188 listed hazardous air pollutants from 174 source categories nationwide. Maximum achievable control technology standards apply to major sources, as well as to area or minor sources.

Megawatt (MW): The practical unit of electric measure equal to one million watts, enough power to supply 330 homes for one hour on a hot summers afternoon.

Megawatt Hour (MWh): Amount of electricity needed to light 10,000 100 watt light bulbs for a one-hour period. One million watts used for one hour.

Midwest Independent Transmission System Operator (MISO): A regional transmission organization approved by FERC in December that operates the transmission system over a large portion of the Midwest. Includes the Cinergy and FirstEnergy systems.

MMBTU: One million BTU (British thermal units)

Multiple Delivery Points: More than one connection into a utility that provides electric transmission service to a wholesale or retail customer. These connections allow service to be fed to a customer from more than one point and can serve as backups in case of a problem with other delivery points.

Municipal Electric Systems: Nonprofit electric utilities owned by municipalities (cities or villages). These utilities are operated and governed by the municipality legislative authority, i.e. the city/village council/board of public affairs elected by municipal residents.

Municipalization: The process through which a municipality assumes responsibility for supplying the electric utility service to its constituents using city-owned facilities. To supply electricity, the municipality may generate and distribute the power or purchase wholesale power from others and distribute it.

Mutual Aid: A network of Ohio municipal electric systems that stand ready to provide assistance to fellow municipal systems when local utility emergencies occur that are too wide-spread to be handled by one system alone.

Network Integration Transmission Service: Transmission service that allows a utility to vary its scheduled power and points of delivery and receipt on a transmission grid without paying an additional charge for each schedule change.

New Source Performance Standards (NSPS): Federal standards of performance for new stationary sources apply to certain industrial processes. States have the option to regulate and enforce these standards. However, if a state chooses not to regulate and enforce the NSPS, the EPA regulates and enforces them. For some categories a "new source" includes any source constructed after .

New Source Review (NSR): A provision of the Clean Air Act that requires older power plants to comply with modern pollution standards when significant upgrades are made.

NOx: Nitrogen oxides

Ohio Municipal Electric Association (OMEA): Formed in , the association is dedicated to protecting the independence and constitutional rights of Ohio municipal electric systems and monitors legislative processes at state and federal levels.

Open Access: The ability of utility companies to use excess capacity available through the high-voltage, long-distance transmission lines of other utilities in return for fair compensation.

Open Access Transmission Tariff (OATT): A tariff approved by FERC that states the rules for purchasing and using transmission service as well as the price of the service.

Parallel Flows: Refers to the flow of electricity over all paths of least resistance when one utility sends energy to another.

Peak Shaving: Power companies price their power according to demand. Because electricity demand is highest at mid-day and during the summer, these are the times when prices are at their peak, but also the time when most businesses consume their most power. To minimize their electricity bills, many customers elect to "peak shave" or cut down on electricity usage during these times of high demand.

PJM Interconnect: A regional transmission organization that operates the transmission system in the Mid-Atlantic states and a large portion of the Midwest. PJM began the first centralized LMP-based energy market. Includes the American Electric Power and Dayton Power and Light systems.

Performance-Based Regulation (PBR): A rate-setting mechanism that attempts to link rewards (generally profits) to desired behavior. PBR sets rates, or components of rates, for a period of time based on external indices rather than as a utility cost-of-service. Other definitions include: light-handed regulation, which is less costly and less subject to debate, and litigation. A form of rate regulation that provides utilities with better incentives to reduce their costs than does cost-of services regulation.

"Postage Stamp" Rate: Rate for electric transmission that does not vary according to distance from the source of the power supply. So-called because postage stamps for mail are typically at a fixed price, regardless of destination.

Power Pool: An entity established to coordinate short-term operations to maintain system stability and achieve least-cost dispatch. The dispatch provides backup supplies, short-term excess sales, reactive power support and spinning reserves. The pool may own manage and/or operate the transmission lines or be an independent entity that manages the transactions between entities.

Predatory Pricing: When a utility offers specific customers special discounted rates, often below its own cost, to entice customers to switch service from a competitor.

Private Letter Ruling: Taxpayer specific ruling furnished by the IRS national office in response to requests made by taxpayers and/or IRS officials.

Private Use: A shorthand expression for federal tax laws that restrict the ability of a publicly owned electric utility to sell and transport electricity to private parties.

Public Utility Holding Company Act (PUHCA): This law prohibits acquisition of any wholesale or retail electric business through a holding company unless that business forms part of an integrated public utility system when combined with the utilities other electric business. The law also restricts ownership of an electric business by non-utility corporations.

Radionuclides: Radioactive chemicals that are usually naturally occurring and found in drinking water. The Environmental Protection Agency has established maximum contaminant levels (MCLs) as part of its enforcement of the Safe Drinking Water Act.

Real-Time Pricing: The instantaneous pricing of electricity based on the cost of the electricity available for use at the time the electricity is demanded by the customer.

Regional Transmission Organization (RTO): A group of utilities in a certain region that combine to jointly plan and study transmission services and develop rules to monitor those transmission services. These groups must be approved by the Federal Energy Regulatory Commission.

Registered Holding Company: A corporation organized to hold the bonds and stocks of other corporations, which the corporation usually controls. The corporation is registered with the Securities and Exchange Commission and subject to regulations spelled out in the Public Utilities Holding Company Act.

Reliability: The degree to which the performance of elements of the electric system results in electricity being delivered to customers within accepted standards, and in the amount desired. Reliability may be measured by the frequency, duration and size of adverse effects on the electric supply (or service to customers).

Renewable Energy Sources: Any source of energy that is continually available or that can be renewed or replaced. Examples include wind, solar, geothermal, hydro, photovoltaic, landfill gas, wood and solid waste.

Resource Efficiency: Using less physical resources to produce the same product or service. Resource efficiency involves a concern for the use of all physical resources and materials used in the production and use cycle.

Restructuring: The reconfiguration of the vertically integrated electric utility. Restructuring usually refers to separation of the various utility functions in individually owned and operated entities. The term is now often used to describe customer choice.

Retail Electric Choice: A system under which more than one electric provider can sell to retail customers, and retail customers are allowed to buy from more than one provider. In Ohio, this was made possible for customers of IOUs by electric industry restructuring legislation enacted by the Ohio General Assembly in .

Retail Market: A market in which electricity and other energy services are sold directly to the end-use customer.

Rotating Over-fire Air (ROFA): Mobotec USA Patented process that is said to provide significant NOx reduction from fossil-fueled power plants without the use of a selective catalytic reducer. This technology includes high inertia asymmetrical injection of combustion air to create high-energy cyclone NOx reduction sites.

Seams elimination cost adjustment: A temporary charge set by the FERC to replace through-and-out transmission pricing, beginning in December and ending in April . It will be replaced by the "license plate" pricing system.

Self-Generation: A generation facility dedicated to serving a particular retail customer, usually located on the customers premises. The facility may either be owned directly by the retail customer or owned by a third party with a contractual arrangement to provide electricity to meet some, or all, of the customers load.

SO2: Sulfur dioxide

State Implementation Plan (SIP): A document that describes the plans a state has proposed to effect compliance with the National Ambient Air Quality Standards (NAAQS). A SIP is required by the federal Clean Air Act.

Stranded Costs: Many utilities argue that under a regulated environment they were required to build generating plants to serve their customers actual and projected needs. If those customers are allowed to purchase power from another supplier under the electric choice provisions, the utilities argue that their investment in generating plants would then be "stranded." Under Ohio restructuring law, the states IOUs were given a transition period in which they could collect stranded costs from customers. This period was essentially extended by the PUCO through rate stabilization plans filed by the IOUs in .

Tagging: The electronic means of scheduling energy transactions over a bulk transmission system.

Time-of-Use Rates: The pricing of electricity based on its estimated cost during a particular time black. Time-of-use rates are usually divided into three or four time blocks per 24-hour period (on-peak, mid-peak, off-peak and sometimes super off-peak) and by seasons of the year (summer and winter). Real-time pricing differs from time-of-use rates in that it is based on actual (as opposed to forecast) prices that may fluctuate many times a day and are weather-sensitive, rather than varying with a fixed schedule.

Total Maximum Daily Load (TMDL): A calculation of the maximum amount of a pollutant that a body of water can receive and still meet water quality standards, and an allocation of that amount to the pollutants sources.

Transmission Access Policy Study Group (TAPS): An association of transmission-dependent utilities and other supporters of equal, nondiscriminatory access to the nation's transmission grids. TAPS members, which include AMP-Ohio and the OMEA, are located in more than 30 states.

Transmission Company (Transco): A company that is engaged solely in the transmission function.

Transmission Loading Relief (TLR): Procedure used by transmission control area security coordinators to curtail energy schedules in an attempt to limit power flow across a transmission system element to avoid exceeding the equipment's peak operating limits.

Unbundling: Disaggregating electric utility service into its basic components and offering separate rates for each component. For example, generation, transmission and distribution could be unbundled and offered as discrete services.

Universal Service: Electric service sufficient for basic needs made available to all members of the populations, regardless of income.

Volt-ampere: The unit of apparent power in an alternating-current circuit equal to the product of the voltage in volts and the current in amperes with regard to phase.

Wholesale Power Market: The purchase of electricity from generators by resellers (who sell to retail customers), along with the ancillary services needed to maintain reliability and power quality at the transmission level.

Want more information on wirewound power resistors wholesale? Feel free to contact us.