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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
Here you go:
Source #1
What does the continuity of capacitor voltage mean?
It might mean that the voltage across a capacitor cannot change instantanteously because that would demand an infinite current.
The current in a capacitor is C.dV/dt so with a finite current dV/dt must be finite and therefore the voltage cannot have a discontinuity.
Why do Americans say ohms per circular mil foot when it's actually ohms circular mils per foot?
A circular mil is a unit of cross sectional area. A foot is a unit of length. Combine the two, getting circular mils foot and you have a measure of the amount of material involved in a unit length of a certain gauge wire.
One interesting use of the amount of material is the resistance of the wire. It makes sense to say "ohms per circular mil foot", because that will tell you the resistance as a function of gauge and length. This is simply a combination of ohms per circular mil and ohms per foot. This basically says that resistance is inversely proportional to cross sectional area, and proportional to length.
Ohms circular mils per foot sounds like its answering a totally different question about the conductor. I don't know what that usage might be.
CommentWe are talking about the US customary unit for resistivity, equivalent to the ohm metre in the SI system.Since the resistivity of a material is given by (RA)/l, dimensional analysis indicates quite clearly that the US-customary unit should be [(ohm x circular mil)/foot] -that is, ohm circular-mil per foot. So, unless we chuck dimensional analysis out of the window, then 'ohms per circular mil foot' clearly isn't correct!
So it remains a mystery to me as to why that's how it is shown in most (but not all) US textbooks. (The SI unit for resistivity, based on dimensional analysis, is the ohm metre -not the ohm per metre). Comments by others would be appreciated!
The primary current on a loaded transformer depends on the secondary current, which is determined by the load. So, if you know the secondary load current, then you can use the turns ratio of the transformer to determine the primary current:
Ip/Is = Ns/Np
Is the dc shunt motor does not have any brushes?
No. A d.c. 'shunt' motor is one whose stator's field windings are connected in parallel with its rotor windings ('shunt' is simply an archic term for 'parallel'); it does not mean that the rotor can function without brushes.
A 208/230 volt single phase motor only has two wires out. It sounds like you are trying to pick up a feed from a 120/240 source that needed a neutral wire to operate. The black and red wire will give you the voltage you need. Make sure that you use a starter and overload protection for the motor.
See discuss question below.
What is the equation for temperature coefficient of resistance?
R= R0 * [1 + rho( t2-t1 ) ]
so from this equation ,
rho= R-R0/[R0(t2-t1)]
where
rho- coefficient of resisivity
R-resistance at any time t
R0- resistance at 00C
t2-final temperature
t1-initial temperature
What is the voltage to ground of 13800 volts line to line?
On a three phase system with a line to line voltage of 13800, a wye connection will give you a voltage of, 13800/1.73 = 7977 volts to ground.
What are the electrical schematic symbols for pumps and for heat tracing?
ELECTRIC symbol for "pump" is usually the symbol just for the motor part of a pump-motor combination. Motor symbol is usually a circle with two opposing tails spinning off the circumferance (kind of like a Hurricane symbol) In the center of the circle is the letter"M" Sometimes the tauils are left off. Heat Trace is usually the same as a heater element: a zig-zag line usually with a note to clarify that is heat tracing.
Explain how to locate the neutral brush position in a dc motor?
leave the brushes of the motor at the position where the induced voltage is zero
What would make the voltage regulator smoke on a 1998 Arctic Cat 500 4x4 ATV?
i have a 1999 having same prob. need info myself . everything checks out good with ststor even replaced regulator. still having same prob.
What is clean earthing system?
A clean earthing system is a circuitry that connects the electric circuit to the ground. This defines the electrical conductors to the Earth's conductive surface.
What is the difference between transformers and adapters?
A transformer is a component that changes AC current from one voltage to another. A transformer consists of two coils, one connected to the input, and one connected to the output. A transformer can convert voltage up or down, depending on the number of windings on the coil. An adapter MAY include a transformer to change the voltage, but an adapter usually changes the voltage AND converts from AC to DC as well, and may have a regulator that locks the voltage to prevent a surge and other components that prevent what is called "ripple".
How many bushing do you get on delta to star transformer?
Your use of the word "bushings" implies you are dealing with a high-voltage transformer (over 600 volt). A three phase STEP-DOWN transformer normally has 3 bushings on the Primary side regardless of whether it is star-delta or another type. The Secondary side might have 3 or 4. A single phase transformer normally has 2 bushings on the Primary side and 2 or 3 on the Secondary side. If the transformer is being used to STEP-UP, it would be reversed from above. If this does not answer your question, I need more info.
What does 40 C mean on a circuit breaker?
"40 C" means 40 degrees CENTIGRADE temperature rating.
The breaker is rated to warm up to this temperature while in use without risk of fire or breakdown. It should not be used in such a way that it exceeds that temperature.
Note that wires connected to the breaker must have an equal or higher temperature rating of its insulation. However, when the wire insulation rating is greater than the breaker rating, the wire's capacity must be determined using the breaker's lower temperature rating.
For example:
If the breaker is 400C and the wire is 400C, the wire capacity would be based on 400C
If the breaker is 400C and the wire is 600C, the wire capacity would be based on 400C
If the breaker is 600C and the wire is 900C, the wire capacity would be based on 600C
I don't believe this to be true... The breaker is tested to and calibrated at the 40c rating. (This has more to do with ambient temp. than the way the breaker is being used) In a case where the temp. may exceed this rating you may trip before seeing the current the breaker is rated. The wire is typically rated @ 75c & 90c and the connection point on the breaker or the lug would be rated @ 60c
The above paragraph is correct It is the ambient rating of the breaker calibrated to trip at that temperature set point. In cold climates this has to be watched very closely. On a -20 C day, on breakers that are exposed to the elements, a breaker on the overload portion of the tripping mechanism may not trip until the current reaches one and a half times the handle rating.
Why cant human power is not hooked up to our tv's to generate our own power?
You can use human power to run your TV. Use a stationary bike tied to a generator. In the TV show "Living with Ed", Ed has just such a setup to generate power to make his toast. Google Bike Generator Plans to see some ideas on-line.
How does the left hand rule apply alternating current generator?
your thumb will point to the diretion of the rotation...and you forefinger will point to the direction of the magnetic flux
AnswerFleming's Left-Hand Rule applies to motors when using 'conventional flow' and to generators when using 'electron flow'. So, assuming you are talking about electron flow, the thuMb indicates the direction of Motion of the conductor relative to the flux, the First finger indicates the direction of the magnetic Field (north to south), and the sEcond finger indicates the direction of the E.m.f. induced into the conductor. This applies whether the generator as an a.c. machine or a d.c. machine.
What are electrolyte plates in a grounding system?
Electrolyte plates in a grounding system are electrically grounded metal plates on which a person stands to discharge static electricity picked up by his body. This is called grounding.
Can an alternator generate high current at low RPM?
good question
An alternator is effectively a small generator. Thus, what you know about generators will also apply to an alternator.
Generator windings are designed to carry specified amounts of current; and a generator is designed to output a given voltage (within a range). If we imagine a generator using field and stator windings that is spinning at less than nominal speed, you will see the terminal voltage begin to decrease. To hold terminal voltage up (thus keep current flowing at the same level at this reduced frequency), the field winding will need to be energized even more (ie, more current pushed through the winding acting as an electromagnet) to increase the mechanical power pulled from the rotating machine. This will overload the field winding at some point (highly dependent on the generator design), and terminal voltage will not be able to be kept at a nominal value without causing damage to the generator.
So the answer to your question is: yes and no. an alternator could provide "high"current into a very small resistance load, but not into a high resistance load (because the terminal voltage will be reduced). The more important thing here is the power your alternator will be able to provide will decay as the speed decays, due to a decaying terminal voltage.
This is one reason for using 60Hz over 50Hz, and 400Hz on ships - the lower the frequency, the bigger (physically) generators must be to generate equivalent amounts of power.
There are other factors that will come into play here as well, such as the reduced RPMs may also reduce the coolling of the alternator, effectively de-rating it.
