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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
How fast can a maglev train go?
because the magnets keep it aloft, meaning theres no friction from the ground
Maglev trains travel so fast because they do not have any wheels or rails to cause friction. This is also due to the fact that electromagnetism is one of the stronger forces in our universe, much stronger than the force of gravity!
Why is it critical you use electrical bonding and earthing?
Earthing, or grounding, is the most important part of an electrical system. It is often overlooked, or questioned because the ground wire is only used, in most cases, during a ground fault event. This is where a current carrying wire touches the ground wire.
When this happens, the electrical path is through the ground conductor, and resistance is lowest. This cause a maximization in current, which in turn causes the upstream fuse or breaker to open as rapidly as possible.
This is why all metal parts around a machine are grounded. If an internal power wire comes into contact, then the current is diverted, and it should not enter the user.
The earth bonding conductor is placed between the neutral and ground buss in a power panel. This conductor provides just a little bit extra resistance between the ground and neutral. In normal circumstances, this slight increase is negligible.
However, during a fault, the current increases rapidly. When this occurs, this little bit of resistance becomes enough impedance to prevent a back feed of the fault current up the neutral before the breaker or fuse can trip.
Of course, this is a simple explanation. But it works for most people.
Electrical generators produce electric power, and generators solve the problem of production. We use electricity in countless ways, and we need to access some kind of generator if we can't directly access the power grid.
How do you limit the current of 3 amp power supply to 1 amp?
You are wagging the wrong end of the dog. A power supply that is constant voltage (the regular ones) may have a LIMIT of 3A at a certain voltage. The reduce the current you either turn down the voltage or add a resistor E=IR to the circuit.
AnswerHow would I do it?I would put together an ancillary, current limiting, circuit which could be connected across the output.
Motor 1 hp equals how many amps?
hp= 745.699872
so if the rated voltage is 220 so 745.699872 /220=3.389 A
What is the difference between a electrical technician and electrician?
There is a little cross over training and math calculations that are the same, but the jobs are very different.
An electrician does residential and commercial wiring, installation, repair, designing, fixing electrical problems, and much more. If you need new lights installed, designing how outlets and power will be laid out in a new home or commercial building, running power to just about everything, making sure power is distributed evenly, the list goes on.
An electronics technician is completely different. They do anything from bench testing equipment, repairing electronics like televisions, CD players, office equipment, stereo systems, computers, pretty much ANYTHING that includes electronics can fit into this field, but most technicians are specialized. A technician who works on consumer electronics like DVD players and televisions will probably not be the same person who does medical electronics like MRI and CAT scan machines. Sure they are both electronics, but work very differently, and require very different training. They can also work with electrical engineers designing new products, testing prototypes, and installing equipment.
There are SOME similarities in training. For example, all of the basic formulas like Ohms law, Lenz law, Kirchhoffs law, etc, are the same in ALL fields that deal with electricity and electronics. But an electrician will learn about home and commercial codes for wiring, standards, and all kinds of regulations meant for the type of work they do. Electronic technicians don't learn those things. They learn circuits, AC and DC fundamentals, components, how they work together, integrated circuits, semiconductors, and more.
Why do they not entirely cross over? Because an electrician doesn't specialize in working on the things an electronics technician does. He doesn't work on consumer, industrial, medical, or other types of electronics by job definition. And likewise, an electronics technician does not design or install electrical wiring in homes and offices.
They are two very different jobs. The only thing they really have in common is the laws of electricity and some components. Both will use electrical wiring and components like resistors, diodes, and capacitors, and both will use the same formulas, but the applications are completely different. Lastly, the laws for electricity are the same in all parts of the world. Ohm's law is the same in America as in Europe, Australia, China, etc.
I know this because I'm in my second year studying for my Associates degree as an Electronics Technician. I am working on designing amplifiers.
How does ac current differ from DC?
AC current fluxuates that is why it is called alternating current. DC does not fluxuate that is why it is called direct current.
Better answer"DC does not fluxuate that is why it is called direct current."If I waggle the voltage control up and down on a d.c. power supply to which a resistor is connected, the current willfluxuate. (Quite poetic, but I prefer to say fluctuate.)
An a.c. changes direction rapidly and continuously, i.e. its direction alternates.
That's why it is called alternating current.
AC current Or alternating current is constantly switching from plus to minus While DC current or direct current moves from minus to plus.
AC and DC refer to Alternating Current and Direct Current respectively. AC is the movement of electrons through a conductor while switching directions, while DC involves electrons moving steadily in a particular direction.
What element fills lightbulbs?
Tungsten
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An inert gas fills the light bulb. The gas is usually argon
Why auto transformer is lighter than conventional type?
because the copper is saved in the auto transformer
that is the ratio of weights of copper in auto transformer to normal transformer is (1-(1/a)) where a is transformer ratio
What are the benefits of ac on dc?
The main advantage of alternating current (AC) over direct current (DC) is safety.
DC locks you onto the current AC throws you away as it alternates.
AC was invented by Nikola Tesla.
Another advantageis that it may be transformed to a very high voltage for transmission over great distances. By doing so the losses due to line resistance are reduced since the current, for a given power, is reduced in inverse proportion.The current is the same going into a bulb as it is coming out.
What is the purpose of using slip rings?
This is the standard answer for both split ring commutator and slip ring.
A split ring commutator is to reverse the current direction through an armature every half turn
A slip ring is to ensure that the current continue to flow to the external circuit
Last bit of additional information.
Carbon brush ensure that the slip ring are in contact with the circuit containing the external load
*Note: Do not get confused with split ring commutator(d.c.generator) & slip ring(a.c. generator)
Does a voltage source have resistance?
Voltage source: is any source that voltage and amperage come from.
Resistor: is any part of a circuit that consumes that energy!
Why zigzag connection in transformer is required?
A zigzag transformer is used in connection with 3 phase and is made up of 6 coils connected in a "Y" manner. Each leg of the "Y" is made up of a coil on a different phase leg of the transformer. The neutral formed by the zigzag connection is very stable. Therefore, this type of transformer, or in some cases an auto transformer, lends itself very well for establishing a neutral for an ungrounded 3 phase system. Many times this type of transformer or auto transformer, lends itself very well for establishing a neutral for an ungrounded 3 phase system. Many times this type of transformer or auto transformer will carry a fairly large rating, yet physically be relatively small. This particularly applies in connection with grounding applications. The reason for this small size in relation to the nameplate KVA rating is due to the fact that many types of grounding auto transformers are rated for 2 seconds. This is based on the time to operate an overcurrent protection device such as a breaker. Zigzag transformers used to be employed to enable size reductions in drive motor systems due to the stable wave form they present. Other means are now more common, such as 6 phase star.
Why are high voltage electrical distribution systems needed in a modern supply system?
For any given load, the higher the supply voltage, the lower the load current. So we use very high voltages on transmission/distribution lines in order for the load current to be low enough to enable us to use conductors of practical size. Furthermore, if we were to use low voltages, the resulting load current would be so high that there would be an absolutely enormous voltage drop -so much so that it would be impossible to transfer the required energy. Low currents also mean less line losses.
If voltage stays the same and resistance increase what happens to electric current?
If voltage increases and the resistance stays the same the current must increase. According to Ohm's Law
V~I (Directly Proportional) and V=RI where R is the constant of Proportionality, Resistance.
Are low-voltage systems totally safe Explain?
No, Their are no electrical systems that are totally safe. Elections harness electricity not control it.
The block diagram of a star delta starter?
The Star/Delta starter is probably the most commonly used reduced voltage starter, but in a large number of applications, the performance achieved is less than ideal, and in some cases, the damage and interference is much worse than that caused by a Direct On Line starter.
The Star/Delta starter requires a six terminal motor that is delta connected at the supply voltage. The Star Delta starter employs three contactors to initially start the motor in a star connection, then after a period of time, to reconnect the motor to the supply in a delta connection. While in the star connection, the voltage across each winding is reduced by a factor of (1 /.'/'3) [1 divided by root three]. This results in a start-current reduction to (1 /.'/'3) [1 divided by root three] of the DOL start current and a start torque reduction to one third of the DOL start torque.
If there is insufficient torque available while connected in star, the motor can only accelerate to a partial speed compared to the full speed it would reach if connected in delta. When the timer operates (set normally from 5-10 seconds), the motor is disconnected from the supply and then reconnected in delta, resulting in full line voltage running currents and torque.
The transition from star connection to delta connection requires that the current flow through the motor is interrupted. This is termed "Open Transition Switching" and with an induction motor operating at a partial speed compared to full load speed, there is a large current and torque transient produced at the poi, unless proper protection methods are used, can cause severe damage to the supply service's infrastructire and to other connected equipment.
If there is insufficient torque produced by the motor when running in star, there is no way to accelerate the load to full speed without switching to delta and causing those severe current and torque transients. These must be allowed-for in the design of the motor and its starting system if they are to have an economic useful life.
Update: Electronic motor-control systems, which offer soft-starts in DELTA configuration, are now replacing the use of manual or semi-automatic star-delta starters.
Technical explanation
When the windings of a 3-phase motor are connected in STAR:
- the voltage applied to each winding is reduced to only (1 /.'/'3) [1 divided by root three] of the voltage applied to the winding when it is connected directly across two incoming power service lines in DELTA.
- the current per winding is reduced to only (1 /.'/'3) [1 divided by root three] of the normal running current taken when it is connected in DELTA.
- so, because of the Power Law V [in volts] x I [in amps] = P [in watts],
the total output power when the motor is connected in STAR is:
PS = [VL x (1/.'/'3)] x [ID x (1/.'/'3)] = PD x (1/3) [one third of the power in DELTA]
where:
VL is the line-to-line voltage of the incoming 3-phase power service
ID is the line current drawn in DELTA
PS is the total power the motor can produce when running in STAR
PD is the total power it can produce when running in DELTA.
- a further disadvantage when the motor is connected in STAR is that its total output torque is only 1/3 of the total torque it can produce when running in DELTA.
For more information please see the answers to the Related Questions shown below.
What is the spark test voltage of glass lined reactor?
In-plant spark testing involves a 6000-volt source, either AC or DC. The voltage potential is applied across the clean, dry glass surface by an insulated, hand-held fault probe. Any exposed metal causes a visible spark to jump between the probe and the flaw, alerting the operator to its location.
While DC testing is preferred method, it can only be used on grounded equipment. Certain glass-lined equipment are totally encapsulated with glass so that they cannot be grounded.
Who was the inventor of fluorescent lamps?
The term "Fluorescent" dates back to approximately 1845-1852 where the English mathematician-physicist George Gabriel Stokes from Cambridge University named this "phenomenon" after fluorite, a strongly fluorescent mineral.
The invention of the fluorescent light is a string of discoveries and developments by many people in several countries. It was developed over 80 years since the invention of the working electric light bulb by Thomas Edison. Like so many things that we take for granted today, fluorescent lighting is the result of numerous small additions to the knowledge and technology of the time.
The development started with experiments in the 1840s by British scientists, George C. Stokes, Michael Faraday and James Clerk Maxwell. A German glass blower, Heinrich Geissler, continued with the experiments and in 1856 produced a vacuum tube that would produce a green glow when a current was passed through it. The tube had little practical value because the green light didn't provide useful illumination. However, Julius Plucker and Alexandre Bequerel experimented with the tube. Bequerel discovered that certain minerals glowed when they were in an operating tube and added coatings to the inside of the tube that would glow.
At the 1893 World's Fair, the World Columbian Exposition in Chicago, Illinois displayed Nikola Tesla's fluorescent lights.
In 1896, Thomas Edison put a calcium coating into the tube and generated useful light. The short life of the tube meant that it never went into production. Nicola Tesla contributed with variations of the tube, again without producing a commercial product. Daniel Moore continued Edison's work and 1904 saw his tubes being used commercially for some limited applications.
In 1894, D. McFarlane Moore created the Moore lamp, a commercial gas discharge lamp meant to compete with the incandescent light bulb of his former boss Thomas Edison. The gases used were nitrogen and carbon dioxide emitting respectively pink and white light, and had moderate success.
An American engineer, Peter Cooper Hewitt (1861-1921) developed the mercury vapor lamp at the same time. It produced yet another green light output so its practical application was limited.
Peter Cooper Hewitt patented (U.S. patent 889,692) the first mercury vapor lamp in 1901. The low pressure mercury arc lamp of Peter Cooper Hewitt is the very first prototype of today's modern fluorescent lights.
In France, George Claude made neon and argon tubes which glowed red and blue respectively. Although it was not of practical use for illlumination, the neon tubes employed electrodes that were longer lasting than others of the time. Fellow Frenchman Jacques Risler added a fluorescent coating to Claude's tubes and his product made it to commercial production.
In Germany, Friedrich Meyer, Hans-Joachim Spanner, and Edmund Germer all worked on low pressure vapor lamps. Although they achieved technical success, their lamp was never manufactured commerically.
General Electric had interests in the new lighting technology and had purchased several patents including Germer's. It came down to George E. Inman and his team of engineers at GE to turn the technology into a commercially viable product. There were a number of legal battles that were fought during the 1920s and 1930s to establish the rights to the technologies. Because of the number of people who contributed to the product, there were numerous patents that affected it. Commercial sales of fluorescent lamps by GE commenced in 1938.
It has been reported that Agapito Flores, a Philippino inventor, received a French patent for a fluorescent bulb and that the General Electric Company bought Flores' patent rights and manufactured and sold his fluorescent bulb (making millions from it). However, all the inventors named above and more predate Agapito Flores' possible work on any fluorescent bulb.
According to Dr. Benito Vergara of the Philippine Science Heritage Center, "As far as I could learn, a certain Flores presented the idea of fluorescent light to Manuel Quezon when he became president. At that time, General Electric Co. had already presented the fluorescent light to the public."
There are other names that do not get mentioned in this brief answer. Each person made their own important contribution and although they are not mentioned, credit should be given to each person who experimented, played, observed and developed the science and technology surrounding the development. Although the early part of the 20th century saw large companies funding and sponsoring inventors and developers, there were many who carried out work without other funding. Perhaps it is the independent experimenters who deserve special recognition for their work.
See the related links below for more information about the history of the fluorescent lamp.
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Why are device run by electrical energy represented as resistors in a circuit?
Resistance is calculated - R (ohms) - primarily as V (voltage) = I (current) times R (resistance) - V=I*R.
It is calculated to determine voltage and current.
It is measured so that it becomes a known value.
Is it possible to have a voltage drop across the energy storage element greater than the supply?
Yes. For a condition called 'series resonance', if the resistance of the circuit is low compared with the inductive reactance and capacitive reactance, then the voltage drop across the capacitor can be VERY much higher than the supply voltage.
Which table in BS 767112008 applies to the current carrying capacity of flat twin and earth cable?
The tables within Appendix 4; "Current-carrying capacity and voltage drop for cables and flexible cords."
4D1 to 4J4. For each type of cable, you will find (with a couple of exceptions) a Table A for current-carrying capacity values and following it, a Table B for voltage drop values.
In what context? Typically people want to know this because someone referred to a residential service as 'two phase', meaning there are two hot wires and a neutral. Technically, there is no such thing as two phase power. Commercial sites are often wired in three phase power, and residences are actually using a special type of single phase power called 'Split single phase'. This has to do with the way the voltage for the hot leads is created. Residential step-down transformers on the ground or on poles use a transformer with a center tapped secondary, making each hot wire about 120 volts. The center tap point becomes the neutral wire. A phase to phase measurement gives you about 240 volts. This is technically created with only one phase from the power generation point, as opposed to commercial services which actually use all three phases. A phase to phase measurement in a commercial service yields 208 volts instead of 240.
AnswerA two-phase system is very rare these days, as it pre-dated three-phase systems. It consisted of a generator with two phase windings, physically displaced by an angle of 90 degrees, giving two phase voltages displaced by 90 electrical degrees. The resulting line voltage is 1.414 times the phase voltage.A two-phase system should not be confused with the split-phase system used for North American residential supplies.
