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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
Does acetone conduct electricity?
It's a temperature dependent variable. Most data sheets from chemical suppliers state the dielectric constant at 25C (77F) as 20.7.
As an aside, the term dielectric constant should only apply to values measured at zero frequency as dielectric permittivity changes according to theoscillationof the applied electric field
What is a DC generator the same as?
A DC generator, or "dynamo", is very similar to a DC electric motor but cannot be described as "exactly the same as a motor" because a DC generator's designed purpose is not to "use" electricity (which a DC motor does) but to "make", or "produce", electricity.
How you will convert kilo volt ampere to brake horse power?
BKW=(Q(m3/hr)*H(m)*S.G.)/(pump effiecency*367)
How many items will a 15kva electric generator support?
In theory, you should be able to load your generator to 15 kV.A (mine stalls far below that load, though!!!). So, divide this figure by the rated output voltage of the generator, and this tells you the maximum current it can supply. The sum of your individual loads should not exceed that value of current. (The current drawn by an individual load is its power rating divided by the supply voltage -just add them up!).
What are advantages of reactive power?
Real power is power that is used to do work. This is the power a light bulb uses to glow. Reactive power is power that is stored in one part of the AC voltage wave, and released in another. This causes the power to appear as a phase shift, and is generally caused by inductive or capactive loads.
With regard to the power system, you can also get reactive power flowing due to unequal source voltages. Under these conditions, the apparent impedance of one source to the other will appear reactive/inductive, resulting in reactive power flow.
Power (Watts) = Current (Amps) * Voltage
Power = 22Amps * 240 Volts
Power = 5,280 Watts
5280
What do you mean by operating voltage of a gm counter?
When you calibrate a GM counter, you run various plots of countrate versus voltage for various energies of isotopes. Since the GM detector runs best in avalanche mode, you pick an operating point in the middle of the avalanche plateau as a compromise for the range of energies you want to be able to detect.
That is the operating voltage.
Keep in mind that, since you are operating in avalanche mode, you cannot differentiate amongst various energies, i.e. nuclides.
If you want to be able to quantify energy, you need to be running in linear mode, and the ion chamber is a better choice. Yes, the GM detector is a form of ion chamber, but it all comes down to sensitivity versus selectivity.
Ohm's original law was 'The potential difference across a conductor is proportional to the current flowing through it, provided physical conditions such as temperature remain constant.'
Today Ohm's law is expressed as E = IR or sometimes V = IR,
the units being Volts, Amps and Ohms.
AnswerOhm's Law ('the current flowing along a conductor, at constant temperature, is directly proportional to the potential difference across that conductor') only applies when the resistance of the conductor is constant so, when verifying Ohm's Law, the temperature must be kept constant, in order to keep the resistance constant.
It should be pointed out that the ratio of voltage (U) to current (R) is called resistance (R), and the resistance of a circuit can be found from the equation, R = U/I whether Ohm's Law applies or not -but Ohm's Law itself only applies when the ratio is constant over a range of voltage variation.
What is the wattage in the circuit?
wattage is voltage and amperage multiplied. example V/A=W or 120v x 20a=2400 watts
What is the value of current in a series when one resistor is open?
Since it is a series circuit with only one path for current, an open anywhere along that single path will cause current flow to be 0 amps.
What device converts direct current to alternate current?
Any device that has a battery and can be plugged into the wall. The power coming from the battery is DC, while the power from the wall is AC.
How do you calculate the conductor size as per the current rating?
transformer rating is not measured based on current..it is also caliculated based on voltage.............ther main losses in a transformer are copper losses and core losses........cu losses mainly depend on voltage and core losses mainly depend on current..........thats why we measure the rating of transformer in KVA(kilo volt ampere)..................
What is the waveform of the output of a half-wave rectifier?
Pulsating dc.
Imagine a sine wave that goes above and below the zero voltage level. A 1/2 wave rectifier clips all the waves either above or below zero voltage. You basically have a hump for 1/2 a cycle then zero voltage for 1/2 a cycle, and then another hump and so forth.
What is the formula to calculate the current carrying capacity of bus bars?
Find out the volume of that object and then the mass of it and divide the mass by the volume to get the density.
Comment:
The answer given above is very wrong(in electricity).
Answer:
Bus bars carry high currents and thus a current transformer is used. It uses the bus bar as its primary winding and its wound section as its secondary winding. The magnetic flux of the bus bar due to its current is very small thus the current in the secondary windings will be small as well and safe to measure with a traditional Ammeter.
NB: These types of work must only be carried out by a qualified electrician. Don't put your life at risk.
Why reactive power is so confusing for engineers?
This is because reactive power concept is completely different from active(real) power,
That is when we talk about active (real) power, we deal with two terms :
The average value, and the instantaneous value.
Both has significant values; let's say the average value is 5kw, where the instantaneous value maybe 2kw or 6kw, etc...
On the otherhand, reactive power has always a Zero average value, and a different significant instantaneous values, but since the instantaneous value is difficult to measure, we always take the maximum instantaneous value of reactive power and deal with it as a textbook terminology (Reactive power) which is symbolized as Q and equals V I sintheta.
And for the same reason (difficult to measure instantaneous value ) we easily deal with the average value of the active power other than the instantaneous value.
As a brief:
(Active power) symbolized P or known sometimes as real power equals V I cos theta
represents the average value.
(Reactive power) symbolized Q equals V I sin theta represents maximum instantaneous value.
Someone can ask!
Why not to take the maximum instantaneous value of average power such as reactive power as a terminology?
Easily , why not to unites the two concepts ?!
This is the answer of our main question (Why reactive power is so confusing for engineers?)
This is easily because ,there is no useful meaning of using the instantaneous value for the active power, because it is a real produced power goes in one direction from source to load, where the average reactive power is always zero valued, since it goes back and forth in the network, and we are forced to deal with it in some way as an indication value and give it a unique terminology to express it as a fact that we cannot skip.
In other words, you cannot compare two different things; apple and banana! Each one has a different taste.
I hope that I answered the question, and dislodged some dust about this confusing concept, even I didn't take the boring mathematical path.
How do you calculate cable size for given load?
Generally speaking, you would find conductor ampacity (the amount of current it can handle continuously) in Table 310.16 of the NEC (National Electrical Code). The numbers in the table are good as long as you don't go over the stated number of conductors at the top of the table and the 86 degree Celsius ambient temperature. If anything changes, use the adjustment factors for conduit fill and ambient temp.
However, with all the possible other applicable sections of the NEC, it really depends on the type of load and howand where the cable is fixed because its operating temperature will depend on whether it is enclosed in a duct, is buried underground or is outside in the open air.
For a typical load, not knowing anything else about it, I would multiply the load (in amps) by 1.25 and find a wire with at least that ampacity.
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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 is alternating current produced?
AC alternating current is generated by magnets spining in a generator at 3000 rpm for 50 hz 3600 rpm for 60 hz (1 pair of north south magnets) 1500/1800 for two pairs and so on,
the magnets move the electrons in the wire- copper (since electrons dont like to be neer each other) they move a very tiny amount then back to where they started <<<>>> motion,
in fact the electrons in the power plant never leave the power planet it is just the electrons moveing each other a tiny amount that creates a current.
How do you Connect 3 phase water heater to single phase?
Most 3-phase welders cannot be made to function on single-phase power. If your welder is an inverter type, such as a Miller Dynasty or Lincoln Invertec, then it may have a single-phase mode with reduced current output. You would have to download the manual for your particular welder. If it is an older transformer (big and very heavy), then you're probably out of options here.
How do you synchronize 2 power generators?
generally the generators are synchrozised by checking three conditions
1. their terminal voltages must be the same
2.their frequencies must be same
3.their phase sequence must be same
if any one of the conditions are not satisfied and they are connected in parallel then the machines will be burnt with in a fraction of second
My boy's Transformer lasted about a year, then broke into several pieces.
What is the importance of threshold voltages and how does it work in a circuit?
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What is the frequency of a 440 volt electrical supply?
The frequency of any alternating current (ac) electrical supply always depends on the frequency at which the supply has been generated.
That is true no matter whether it was generated at a power station, for use in a home or factory, or in a dc-to-ac power inverter unit, for use in, say, a vehicle or boat.
Power stations in USA, Canada and other countries generate ac at 60 Hz.
Power stations in countries in Europe and other world areas generate ac at 50 Hz.
"Hz" is short for "hertz" which is the name used internationally for "one cycle per second".
Breifly explain about reactive power in electric circuits?
Reactive power is opposite to Active power. The vector sum of these two powers is apprant power. So reactive power is vector difference between Apprant power & actual power given by
Reactive power= Root of (difference between squares of apprant & active power).
It is lost power of the system on which power factor depends.
What will be the cable size for 300 A if the 3 phase voltage is 220 volts?
At least 50mm but with all the de-rating factors it might be 70mm that's if its 2 cable single phase non armoured clipped direct. Check out the tables dopey!!!!
FYI 50 mm = 2 inches, 70 mm = 2.75 inches these are not wire sizes, sound more like cable outside diameters.
Correct answer
The wire size is dependant on the insulation factor on the wire. A few common insulations and corresponding wire sizes for 150 amps are - Size 0 R90 good for 155 amps, also with insulations of RW 75, TWH, TW75, good for 150 amps. Size 000 TW good for 165 amps.
What is the significance of the constant temperature reference in ohms law?
As temperature affects resistivity, the resistance of a conductor may change if its temperature is allowed to increase. For pure metal conductors, the resistance generally increases as the temperature increases.
Ohm's Law ('the current flowing along a conductor, at constant temperature, is directly proportional to the potential difference across that conductor') only applies when the resistance of the conductor is constant so, when verifying Ohm's Law, the temperature must be kept constant, in order to keep the resistance constant.
It should be pointed out that the ratio of voltage (U) to current (R) is called resistance (R), and the resistance of a circuit can be found from the equation, R = U/I whether Ohm's Law applies or not -but Ohm's Law itself only applies when the ratio is constant over a range of voltage variation.
