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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
The electrical power dissipated by a resistance R is?
Power, P, is current, I, times voltage, E. (P = IE)
Not knowing one of voltage, E, or current, I, you can apply ohm's law ...
E = IR or I = E/R
... and come up with variations ...
P = I2R
P = E2/R
Typical height ranges from 15 to 55 metres (49 to 180 ft), although heights in excess of 300 metres (980 ft) do exist. Check Wikipedia out for more info.
I needed to know the heights so I could compare wind turbine proposals with something already in the landscape.
What are the 6 types of phase change?
melting, vaporization, sublimation, condensation, freezing, and deposition are six types of changes in matter.
To be sure, you need to contact the utility. My guess from your description is this is not really deemed high voltage. It is most likely a distribution to sub transmission voltage (2.4kV - 69kV); If it were higher than this, it is very likely that the utility would have purchase agreements or own the property directly under the line for 30-80 feet either side. this is very typical in rural farming areas. The utility often allows farmers to farm right up to structures...but if anything goes wrong (such as a crop duster clips the line), the utility has every right to come in and grind the crops to dust in the process of repairing the line.
Is electrical engineering dangerous?
Electrical engineering is a large field. Certain jobs can be dangerous; others are not so dangerous. If you know what you're doing and are careful, the risks tend to be minimal.
What is green field substation?
In my line of work that is an Electrical High Voltage substation that is brand new. It is being built from a green field into an energized fully functional substation yard. There is no existing substation or remodeling of an existing one being done.
In a tank circuit why can be the energy across the inductor and that of the capacitor not be equal?
When an LC tank is excited at the resonant frequency, the energy across each will be equal (but not necessary equal at a given moment in time). If excited at a frequency other than the resonant frequency, the impedance of the inductor (wjL) and capacitor (1/wjC) will not be equal, therefore energy across each will be different.
this type of supply use in satrter,
it is a supply, when we are disconnecting our main supply ,it continue oue operation for few time.
that means a way is make for the supply of our operations
In a series circuit why does the largest voltage drop occur across the largest or smallest resistor?
It doesn't.
In a series circuit, the largest voltage drop occurs across the largest resistor; the smallest voltage drop occurs across the smallest resistor.
Explain the power flow diagram of induction motor?
The input power, Pin, is reduced by different loss sources in the system. These reductions are the difference between input power & output power.
The losses are:
PSCL: Stator copper losses, or I2R losses
Pcore: Core losses
PRCL: Rotor copper losses
PF&W: Friction & windage losses
Pmisc: miscellaneous losses
All of these losses reduce the input power. The output power is the input power minus all of the losses.
Pout = Pin - PSCL - Pcore - PRCL - PF&W - Pmisc
Many mutlimeters have this capability. You'll probably want a digital multimeter. If you do a good search, this should be easy to find. You'll need to read through the specifications carefully to make sure you find one that gives the level of accuracy you're looking for. the more accurate it is, the more you'll pay.
What is output frequency sync to mains?
this always used in inverters and UPS As in standby UPS And line interactive UPS ,the output frequency must be always track the input frequency as it supply the load from utility in standby mode, for any change that will affect the load .
as example the frequency of the utility was with permitted values say 58Hz and suddenly the main power cutout, so UPS must be on same frequency so when convert to backup stored power mode ,the load doesn't affected and power continue to supply the load from the batterys through inverter , so output frequency must be always synchronized to utility frequency (mains) in case of any fault happened, hope i answered your question.
Sherif Salah
R & D Engineer at Arrow Electronics
Egypt
What is the function of Variac?
Variable auto transformer or Variac also has the same function as regular transformers but handle lower voltages. The Variac is equipped with an automatic switcher to automatically step the voltage up or down.
It is a round power transformer with a sliding contactor which you attach 110 volts Ac to it's input terminals and can adjust the output connector voltage contacts from about 2 volt to 140 volts. Very useful in design and testing things. They do have a current limit rating so make sure you have one that will supply your highest current need.
Does 10BaseT cable need terminators?
Every transmission line requires termination, either in the form of the ultimate load, such as an antenna, or in the form of some kind of resistor. 10BaseT is no different.
However, that termination is usually built in to the device in which the cable is plugged. This is different from older systems, such as ArcNet, where the coax cable requires termination on each of the far ends. This is because the 10BaseT system is a star system rather than a partial ring system, so the termination is not a function of the chosen topology.
The reason termination is required in a transmission line is that every step change in characteristic impedance encountered by the wave front as it propagates through the line results in some kind of reflection back towards the source. These reflections result in distortion, loss of power, even damage to the transmitter or circuit.
To reinforce this understanding, consider the 75 Ohm coax cable typically used in a television distribution system. In the simplest case, you connect a cable from the service entrance to the TV set, and you are properly terminated. If, however, you use a splitter, such as for a TV set and a VCR, you now have three transmission lines, one to the splitter and two from the splitter. Is the RF output of the VCR connected to something? It should be, either to a TV set or to a terminator, otherwise there will be problems due to ringing, interference, ghosting, etc.
What is the formula for calculation of wire resistance?
R = resistance = rho * L / S
rho is resisitivity in [Ohm m], it depends on the material (Copper: 2e-8 [Ohm m])
L is wire length [m]
S is wire cross section [m]
EDIT: for high frequencies, you may also wanto to take sink effect into account (~MHz)
Explain the working principle of turbo generator?
The working principle of a turbo generator is that of forcing extremely hot condensed air into the piston chamber. The hot condensed air reduces the need for fuel.
What is the difference between a motor starter and a contactor?
Motor started will have overloads the contactor connect es line voltage.
How do you ctmm motor protection relay setting?
Just calculate from motorplate: Watts/(Square3*V*cosP)=> example motorplate says: 4.7Kw 440V cosP: 0.82 4700W/(square3*440V*0.82) here you get minimum setting for motor, this case 7.5A
JT
Do modern homes use electricity that is arranged in series or in parallel circuits?
In a modern home you use parallel circuit's. The reason why they are parallel circuit and not series is For example: say your kitchen light goes off, if that light goes off the others in your house won't. They also use parallel circuit in schools.
However, when there is a switch in the circuit, that switch is in series with the load, so you could say that electrical wiring is arranged in series-parallel.
