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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
What are Conduction Current Density and Displacement Current Density?
We know specifically the definition of current density as current flow through a surface of unit area.
Conduction current is the current through the conductors in the presence of electrostatic fields and displacement current is the current flow due to time varying electric fields
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.
Are potential difference and voltage always the same?
Voltage is simply another word for potential difference.
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
What is the difference between a motor starter and a contactor?
Motor started will have overloads the contactor connect es line voltage.
120 v
What happen if the number of loops in the primary and secondary coils in a transformer are the same?
If the number of turns in the primary is the same as the secondary, this would be an isolation transformer. Primary and secondary voltages should match (minus the inherent transformer losses), as should the current.
How do you calculate volt drop with length and resistance?
cable length multiply with the design current and multiply again by mV/A/m (check on site guide) then devide it by 1000. then u will get the volt drops. BY; MAMERGA
Why The Excitation current is non-sinusoidal when applied voltage is sinusoidal?
excitation voltage is sinusoidal because it is taken from the terminal of alternator but excitation current is non-sinusoidal because it always dc.
4 megawatts - heaps
The megawatt is equal to one million watts. Many events or machines produce or sustain the conversion of energy on this scale. For example: lightning strikes, large electric motors, naval craft (such as aircraft carriers and submarines), engineering hardware, and some scientific research equipment, such as supercolliders and large lasers. A large residential or commercial building may consume several megawatts in electric power and heat.
Overhead cables are made of almunium not of copper explain?
Much of the newer overhead cables is made of aluminum with steel reinforcing it for strenght purposes. Aluminimum is much cheap, and much lighter, thus it is cheaper to use vs. copper for high voltage transmission, and copper has a lower resistance which means more electricity can get through the wire/ cable, which means more electricity can get around the world quicker. most people should use copper becasue it has a lower resistance where aluminuim has a bit of a high resistance not to much but a bit so that is why you use copper not alominuim.
What is difference between cold load and hot load?
hot load occurs when the power is high and the cold load occurs when yhe power is low
What are time delay relay characteristics?
Time delay protective relays used in the power industry can be time over current or voltage, or definite time over / under voltage / over current.
Definite time type relays use an over / under voltage / current element that picks up when voltage / current reach a specified level. When this picks up, a timer is started. If current / voltage stays above / below the pickup value for long enough to allow the timer to expire, the relay trip contacts are closed.
Time over current elements use an inverse time - current curve to define speed of operation, so the more current is present, the faster the relay will operate.
How does the number of wraps of wire affect the strength of an electromagnet?
The more turns of wire in an electromagnet the stronger the magnetic field.
Nikola Tesla invented the poly-phase induction motor in 1883.
Difference between line transformation ratio and transformation phase ratio?
line transformation ratio would be the turns ratio (ie voltage ratio), while the phase transformation ratio is most probably the phase shift introduced by a 3 phase transformer.
What is the conversion for rms power to peak to peak power?
RMS power is Peak-To-Peak power divided by the square root of 2.
This definition, however, only holds true for a non-reactive, or resistive, load, with a power source that is truly sinusoidal.
For a open circuit the VSWR is?
the voltage standing wave ratio is defined (1+p)/(1-p), where p is the the reflection coefficient magnitude. p = 1 for an open circuit, therefore the VSWR will approach infinite.
