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Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
Describe chromel alumel thermocouple extension wire?
Sometimes prior to June, 1953, Professors E.A. Farber and J. R. Akerman, of the University of Wisconsin, observed in a particular instance that two thermocouples made of hte same material and exposed to the same temperature simultaneously, gave different electromotive force (EMF). A natural question to arise from this observation was "Does the method of making the thermocouple junction have an influence on the EMF produced?". This experimental work was undertaken in an endeavor to find an answer. Preliminary experimental work indicated that there were reproducible differences between thermocouples manufactured by various methods. For more extensive experimental work, various heat treatments were investigated in addition to various methods of junction manufacture. Chromel-alumel and iron-nickel were the two metal combination used. Chromel-alumel was chosen because a combination of pure metals might be affected differently than a combination of alloys. The extremes of temperature under which the thermocouples were tested were -300¡ãF and 1000¡ãF. These temperatures were somewhat arbitrary, but the object was to subject the measuring junctions to temperatures considerably above and below the reference junction temperature of 32¡ãF. Tests were conducted with thermocouples whose junctions were formed by (1) twisting, (2) pinch welding, (3) silver soldering, (4) aceylene welding. Thermocouples made by these four methods were tested as manufactured, that is, no heat treatment of any kind, after subjection to 650¡ã F for twelve hours followed by slow cooling in the furnace to 300¡ã F or below. Briefly, the differences between EMF developed by thermocouples made by different methods, at a given temperature, are small and not reproducible. Thus was unexpected in view of the preliminary experimental work. At any temperature between 32¡ã F and 1000¡ã F the greatest EMF difference between chromel-alumel thermocouples made with various junction types corresponds to about 3.5¡ãF; between 32¡ã F and -300¡ã F the greatest difference corresponds to 5¡ã F. The corresponding figures for iron nickel are 6¡ã F and 10¡ã F. The commercially pure metals iron and nickel do not produce thermocouples less affected by (or, sensitive to) junction type than do the alloys chromel and alumel, if sensitivity is based on a comparison of differences in EMF generated. If comparison of temperature differences corresponding to EMF differences is the basis, iron-nickel thermocouples are more sensitive than those of chromel-alumel. Heat treatment had some effect on EMF-temperature relationship, but not very much. In instance where heat treatment had a definite effect, it was to increase difference between the maximum and minimum EMF by about 20% at 1000¡ã F for chromel-alumel thermocouple. At -300¡ã F apparently metallurgical changes occurred which affected the EMF-temperature relationship, but at a slow rate. Two to four hours were necessary for some of the chromel-alumel thermocouple to give an EMF that was unchanged with time, at a given temperature. At a temperature of approximately -300¡ãF, the temperature indicated by several of the chromel-alumel thermocouples change approximately 3¡ãF in one and a half hours, while other chromel-alumel thermocouples indicated no change at all or indicated a change in the opposite direction. In general, the difference in EMF between chromel-alumel thermocouples of various junction types and best treatments are considerably less than tolerance allowed by most manufactures of thermocouple wire. Since there was not much difference between the EMF generated by thermocouples with different type junctions, an endeavor was made to find out what would produce a decided difference in EMF. A number of chromel-alumel thermocouples were made with both twist and silver solder junctions, the junctions of each type being made as nearly alike as possible. A number of thermocouples were made with both twist and silver solder junctions, the junction of each type being of different quality. The difference in quality of twist thermocouples was produced by varying the tightness of twist, by not cleaning the wire before twisting, and by peening the junction after twisting. The difference in quality of the silver solder thermocouples was produced by not cleaning the wire before soldering, by peening the junction after fabrication, and by heating the wire to a temperature much higher than necessary during soldering. The twist thermocouples with junction of non-uniform quality produced EMF with no greater differences than EMF produced by twisting thermocouples of non-uniform quality produced EMF with no greater differences than EMF produced by silver solder thermocouples with uniform quality junction. It was thought that a smaller wire size might be more sensitive to quality of junctions than the wire size used in all the above work. Silver solder thermocouples were made of 28 B & S gauge chromel and alumel wire, and both uniform and non-uniform quality junctions were formed. For the 28 B * S gauge wire, the uniform quality silver solder junctions had a maximum EMF difference between thermocouples of 0.005 mv (equivalent to 0.55 ¡ãF) and 0.013 mv (equivalent to 0.055¡ãF) at -300¡ãF and 1000¡ãF respectively. The non-uniform quality silver solder thermocouples made of 28 B &S gauge wire had a maximum EMF difference between thermocouples of 0.009 mv (equivalent to 1¡ãF and 0.008 mv (equivalent to 0.34¡ãF) at -300¡ãF and 1000¡ãF respectively. From this limited data, it appears that 28 B & S gauge wire is more sensitive to junction quality than is 20 B & S gauge wire, which was used for all the rest of the experimental work. Copyright 1957
University of Wisconsin-Madison
What are the multiple resistance circuits?
Multiple resistance circuits are electrical circuits that contain more than one resistor connected in various configurations, such as series, parallel, or a combination of both. These circuits are commonly used in electronic devices and systems to control the flow of current and voltage. The total resistance in a multiple resistance circuit can be calculated using different formulas depending on the arrangement of the resistors.
How is electricity transported?
Electricity is transported over long distances through power lines, which are made of conductive materials like copper or aluminum. The electricity flows from power plants to homes and businesses through these lines, and transformers are used to step up or step down the voltage as needed for efficient transmission and distribution.
Derive the output equation of DC machine in terms of its main dimensions?
The difference between AC and DC has to do with the direction in which the electrons flow.
In DC, the electrons flow steadily in a single direction ("forwards").
In AC, electrons keep switching directions, sometimes going "forwards" and then going "backwards."
Is death more dependent on amperage or voltage?
High amperage with low voltage won't conduct through tissue. High voltage with low amperage will conduct through tissue but will not cause tissue damage.
Voltage must be high enough (at least 70-80V) to conduct and interrupt nerve conductivity. Amperage must be high enough to damage tissue. Less than 1/2 milliamp no sensation
1/2 to 2 milliamps Threshold of perception
2 to 10 milliamps muscular contraction
5 to 25 milliamps painful shock (may not be able to let go)
Over 25 milliamps Could be violent muscular contraction
50 to 100 milliamps Ventricular fibrillation
over 100 paralysis of breathing. Both are dangerous, because you can't have one without the other.
amperage = voltage / resistance
If you have something with a fixed resistance (for example, your heart) the amount of voltage will be directly related to the amount of amperage. Double the voltage, and you would get double the amperage.
How does a Potential Relay Work?
I am going to post an article published in 2006 by John Tomczyk of Ferris State University, Big Rapids, Mich. I cannot improve on his description.
The Potential Start Relay
Figure 1
This month's article will cover theory and operation of potential starting relays. The article that will appear in the Aug. 7 issue will cover potential relay ratings and specifications along with systematic troubleshooting.
Potential or voltage starting relays are used with single-phase capacitor-start/capacitor-run motors, which need relatively high starting torque. Their main function is to assist in starting the motor. These starting relays consist of a high-resistance coil and a set of normally closed contacts. The coil is wired between terminals 2 and 5, with the contacts between terminal 1 and 2. Terminals 4 and 6 are used for capacitor and/or condenser fan connections and have no electrical significance to the starting relay itself (Figure 1). Terminals 4 and 6 are sometimes referred to as dummy terminals and are simply used for wire connections.
Fig. 2 shows how a potential starting relay is wired to a capacitor-start/capacitor-run compressor motor. Note that the relay coil is wired in parallel (across) the start winding. The normally closed contacts are wired in series with the start winding and the start capacitor.
OPERATIONWhen the power is applied through the cycling control, both the run and start windings are energized. The start and run capacitors provide the phase shift for starting torque because of their capacitance adding when wired in parallel.In fact, both capacitors are wired in series with the start winding and in parallel with the run winding. The run capacitor also limits the current that will pass through the start winding when the motor is running, since they are wired in series. The run capacitor also provides running torque when the motor is up and running.
The operation of the potential starting relay is based on the increase in back electromotive force (back EMF) or a bucking voltage that is generated across the start winding as the motor increases in speed. The large metal mass of the motor's rotor turning at high speeds with motor windings in close proximity has a voltage generating effect (Figure 3). This generated back EMF opposes line voltage and can be measured across the start winding or across the coil of the potential relay at terminals 2 and 5. The back EMF is usually a higher voltage than the line voltage and can be in the 400-V range. All motors have different magnitudes of back EMF.
Figure 2
The back EMF voltage generated across the start winding causes a small current to flow in the start winding and in the potential relay coil since they are in the same circuit. When the back EMF has built up to a high enough value, referred to as pick-up voltage, the contacts between terminals 1 and 2 will be picked-up opened. This will take the start capacitor out of the circuit.
The pickup voltage usually occurs when the motor has reached about 3/4 speed. The start winding is still in the back EMF circuit keeping the relay's coil energized while the motor is running at full speed.
When the cycling control opens, line voltage power is taken away from the motor. The motor's rotor decreases in speed, thus the back EMF generated across the start winding decreases in magnitude. The relay now sees a lowering back EMF and no longer can generate enough magnetism in its iron core to keep contacts 1 and 2 open.
Figure 3
The contacts thus return to their original normally closed position by spring power as the motor coasts to a stop. With the start capacitor out of the circuit, the motor now becomes a permanent split capacitance (PSC) motor in the running mode only.
John Tomczyk is a professor of HVACR at Ferris State University, Big Rapids, Mich. He can be reached by e-mail at tomczykj@tucker-usa.com.
Publication date: 07/03/2006
When the conversion of a system, process, etc. Is completed in phases rather than a complete transformation at one time.
Solar inverter modifies the electricity from the solar panels and changes it to power the appliances in a house. This inverter has a special feature that can adapt for use with photovoltaic arrays.
How do system grounding and equipment grounding differ?
"System grounding" refers to the protective fuses or circuit breakers fitted inside the main panel which protect the service wiring for any particular external site or inside a particular building.
"Equipment grounding" refers to the provision of protective grounding wires within any individual piece of equipment which is not of the type that is "double insulated".
Taking the US as an example: in any modern home's wiring for socket outlets there are up to three wires in play.
Look at the the common three-prong plug:
The two slotted prongs carry the current back and forth to your appliance, from the "hot" to the "neutral".
The U shaped prong - the equipment ground - is used to help protect the home from the wiring overheating and catching on fire - or you from getting a shock - from a malfunction in the appliance.
It works like this: if a faulty connection occurs inside an appliance, either from material deterioration ("old age" caused by crumbling or burnt-out insulation) - or from an accident such as dropping an electric kettle onto a hard floor - it could start a home fire no matter what voltage it runs on, or could kill you if the voltage is higher than about 50 volts.
To help prevent this, an equipment ground wire is attached to any exposed metal casing so that, when properly working, there will be no current in the equipment ground because it is not connected to the hot wire.
If ever the hot wire makes contact with the exposed metal casing or the equipment ground wire, that would immediately cause a large surge in electrical current and that surge would blow the protective fuse (if one was fitted inside the appliance) or would exceed the rated allowed running current rating of the branch circuit breaker and cause it to trip off. Thus the flow of current to the equipment would be quickly turned off.
How do you convert single phase supply to three phase for running a 3-phase motor?
Any business, such as a factory, or any home needing a 3-phase supply for some equipment would usually get that supply by having it installed by their local electric power utility company.
For a very small 3-phase motor, solid state power inverter units are available nowadays which can be powered from household 1-phase supply.
If you want to know how to convert a 1-phase to a 3-phase supply for high power applications it can be done using a motor/alternator set or a solid state inverter unit but to use these safely requires specialized equipment and electrical engineering knowledge. The full answer is too complicated to explain here.
Depending on the amount of money you want to spend to make this happen there is a device on the market called a VFD ( Variable Frequency Drive). On the three phase input terminals you apply your single phase voltage. On the output terminals you connect your three phase motor. When run in this configuration there is an internal switch that has to be changed to let the VFD know that it should be looking for only two lines on the input to be hot. Other wise the VFD thinks that there is a line loss on the three phase input terminals and the unit will not start.
Before you do any work yourself,
on electrical circuits, equipment or appliances,
always use a test meter to ensure the circuit is, in fact, de-energized
IF YOU ARE NOT REALLY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.
Assuming the single core cable forms part of a three phase circuit (i.e. you are clamping three single core cables) it is best to install the three cables close togther in what is called "trefoil" formation. This harmonises the Eddy currents of each phase.
What is another word for the North Star?
The name of the north star is Polaris. As the brightest star in the constellation of Ursa Minor it is also called alpha Ursae Minoris. It is actually a multiple star comprised of Polaris Aa, Polaris Ab and Polaris B.
In North America the most common distribution for new homes is 200 amps. Services larger than 200 amps have to get written permission from the utility company. Along with approved drawings that have load calculation filled in as to the exact connected load. In my work career I have only installed one 400 amp service in a very large home.
How do you wire a 3 wire 220-240 volt power feed to power a 4 wire 220-240 volt submersible pump?
If you asked this question because you have no experience of working on the latest household power circuits and you hope to get enough information on this site to be able to do the job properly and safely, it is best to warn you not to rely on getting accurate information from this site about such a potentially dangerous subject.
By asking this question you probably aren't quite ready to take on this particular task.
Really, don't do this one yourself. Electricity is far too dangerous to handle if you don't already know your local Wiring Codes or Regulations or you have not been trained how to do this work.
How to do this job depends entirely on the Wiring Codes or Regulations for the locality (Town/State) and on the exact location of the appliance you wish to hook up. If it is anywhere that is subject to water splashes or spray - such as in any room supplied with running water pipes, like a kitchen, bathroom, shower room, etc., or in a pool-side area - in many places nowadays it is actually illegal to attempt to do this kind of work unless you are already a licensed electrician.
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The four wire pump has 4 colors, Red (L1), Black (L2), Green, and Yellow. These connect to the control box for the pump often fed from a double throw breaker with 10 gauge wire. The juice is 230 volts (Well technically, volts are not juice, current is juice, but you might not be around to argue the point). This is more then enough to kill you, and the breakers will NOT protect your life. Handling a wet pump makes your body have less resistance, and the current through your heart will stop your heart, and cause muscles to fully contract, including your heart.
For your safety and that of anyone else who may to use the appliance, ask a professional licensed electrician to advise you or to do the work for you.
IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.
If you do this work yourself, always turn off the power
at the breaker box/fuse panel BEFORE you attempt to do any work AND
always use an electrician's test meter having metal-tipped probes
(not a simple proximity voltage indicator)
to insure the circuit is, in fact, de-energized.
How do you increase or decrease voltage?
This question makes no sense as written. However, maybe it will help to know that for a given load if you increase voltage the current increases proportionally and if you decrease the voltage the current decreases proportionally. Ohm's Law says Voltage = Current x Resistance.
Where is Mercury Cougar 1995 fuel switch?
the fuel reset switch is located in the truck of the car, drivers side (left side) behind the trunk side cover, you have to remove the carpeted cover to access the relay reset (theres a red button on top)
What is the approximate horsepower rating of a 240V motor that draws 15.5A of current?
A motor that draws 14 amps on 240 volts is probably a two horsepower motor, but it could be three depending on the efficiency.
Watts = amps x volts. There are 746 watts in 1 horsepower.
CommentIn North America, horsepower is always used to describe the output power of a motor. You can only find the input power by multiplying the supply voltage by the load current. You will, unfortunately, then need to know the efficiency of the machine to determine its output power in horsepower.
How do you determine the amperage given the voltage and power dissipated?
Like Ohm's Law, the formula for calculating power is a simple product of two quantities. It is given by the formula P = VI, where V is the voltage in volts and I is the current in amperes (or simply amps). So, if you know the value of any two of the quantities, you can easily calculate the third with simple arithmetic. For example, if the current flowing through a resistor is two amps and the voltage drop across that resistor is five volts, the power dissipated by the resistor is, P = VI = 5 volts * 2 amps = 10 watts. If you are given the power and the voltage, you can easily find the current. For example, if you are told that the voltage drop across a resistor is five volts and is dissipating 10 watts, the current through the resistor is 10 watts/5 volts = 2 amps.
How do you calculate earth leakage current for certain load example 5KW motor 660Vac?
There are many factors that determine what the leakage current will be. You could find out what the insulation winding resistance of the new motor should be and use the 660 volts and Ohm's law to calculate the current. If you measure this using a DC insulation tester however it probably will not yield an exact measurement since the test is not under normal operating conditions, but is a DC voltage test. To get the best measurement you really need to test the motor under operation and use a leakage clamp on the ground connection to see what the current really is since other factors come into play such as the insulation resistance, imbalance and frequency. An example of a tool would be the Fluke 1630 or Fluke 360.
In a wet type of voltaic cell what is electrolyte?
In a wet type of voltaic cell, the electrolyte is a liquid or gel substance that allows the flow of ions between the two half-cells to maintain charge neutrality. It helps facilitate the flow of electrons in the external circuit, allowing the cell to generate electricity. Examples of electrolytes in wet cells include acidic or alkaline solutions like sulfuric acid or potassium hydroxide.
Why relay contact haS two different ratings for AC VOLTAGE and DC VOLTAGE?
AC IS +/- WHILE DC IS JUST A LEVEL AC120 MUST WITHSTAND THE PEAK VOLTAGE
Reply: How is putting the two sets contacts in series going to help?The same potential is still being broken at the first set of contacts.>-------------0___0--------0___0---------->Parallel would make more sense to me, since then the current would be split between the two sets of contacts.
What is working principle of Auto blood analyser?
Auto blood analyzers work by using specific reagents to analyze the different components of blood, such as red blood cells, white blood cells, platelets, and various biochemical markers. These machines automate the process of sample preparation, analysis, and data reporting, allowing for faster and more accurate results compared to manual methods. The analyzers rely on various techniques like spectrophotometry, impedance, and flow cytometry to detect and quantify blood parameters.
What is the difference between earth and neutral?
It is there to force a fuse to blow or a circuit breaker or GFCI to trip if a fault condition occurs in any appliances, their flexible cords or plugs that are connected into the circuit.
By carrying away the excess current in a fault condition - which should cause the protecting fuse to blow or circuit breaker to trip - the "ground" or "earth" wire protects the building and its occupants because the power should be cut off before anyone gets electrocuted or any overloaded circuit wiring or appliances catch on fire.
The neutral is the normal "return" wire: in systems where the load is supplied from only one hot (or "live") wire, the neutral completes the circuit and carries current back from the load to the power station.
All the neutral and ground (or "earth") wires in a building are tied or linked together at the incoming service main breaker panel. This is the only place they should ever be tied togetherbecause it is "upstream" of all the fuses and/or circuit breakers protecting the hot (or "live") wires for the various circuits installed in the building.
Warning: we must never assume that a neutral is safe to touch: it has to be checked with a voltmeter or a voltage indicator to be sure it is not "live". This is because a neutral wire is designed to carry current under normal circumstances.
So, if a neutral wire going back to the incoming main breaker panel has not been properly connected - or suffers a deliberate disconnection or some accidental damage which causes it to break - then it and any neutral wires connected to it further downstream will go live up to the break because of being connected to the downstream loads which still have hot feeds coming into them!
That is why we should never use a neutral as a substitute for a proper, separate, ground or "earth" wire.
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If some external accidental damage or electrical breakdown of the wiring's insulation occurred anywhere to the house wiring, to a socket outlet or to an appliance, these things could be very dangerous if there was no such protective wire.
For example, if there was no protective ground or earth wire, a fault could happen that is of a kind which did NOT draw enough extra current to blow a fuse or make the main circuit breakers on the incoming supply panel "trip" to cut the current off - but the wiring could still catch on fire and/or someone could be electrocuted!
Neutral wires are the return paths to the power generation station for current it supplies to the house or building via single live or "hot" wires in the branch circuits.
For more information please click on the Related Questions below.
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Earth (also called protective ground or ground) and Neutral are normally both near 0 volts to ground potential. The neutral service wire is designed to carry current and the "ground" or "earth" wire is designed so that it should carry no current unless there is a fault.
In North American 120 volt single-phase services, earth and neutral are connected together at each service entry and connected to the earth by a stake in the ground or other reliable grounding means. They are not connected at any other point inside the building. The neutral wire ends at the transformer near the building and does not connect back - via the distribution lines - to the power utility company's generating station(s).
In North American Electrical Engineering and code, the terms "neutral" and "ground" are not officially used. The formal term for neutral is the "grounded" conductor and the term for the earth or ground connection is the "grounding" conductor. Since these are easily confused, it is more common to use the terms neutral and ground.
In North America a 240/120 volt so-called "split single-phase service" from a center-tapped 240/120 volt utility service transformer is often used for major home appliances - such as ovens, ranges, water heaters, clothes washing machines and driers, air conditioning units, etc. - which take a high power draw.
They work as follows: the main heaters and/or motors run on 240 volts single-phase delivered from two "hot" wires. (Usually one hot is colored red and the other hot is colored black.)
If they include some low-power devices - such as time clocks, wash-cycle programmers, etc. - that only need 120 volts, the current for them is delivered from one of the above-mentioned red or black "hot" wires. A separate wire called a "neutral", which is normally colored white, is used to send the current from those small 120 volt devices back to the center-tap on the 240/120 volt service transformer.
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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.
Before you do any work yourself,
on electrical circuits, equipment or appliances,
always use a test meter to ensure the circuit is, in fact, de-energized.
IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.
How does the load affect voltage output of a series generator?
In a series generator, the voltage output is directly affected by the load. As the load increases, the voltage output decreases due to increased voltage drops across the internal resistance of the generator. Conversely, reducing the load will result in an increase in the voltage output.
How can a silica gel pouch get busted in a container?
The plastic in which the silica gel is sealed is usually very tough. (That's why it was chosen.) It's also "stretchy" enough to withstand a good bit of compression without failing. (You could stand on half of a pouch and it wouldn't rupture.) The most probable method of failure of the pouch is that it was cut or punctured in some way.
