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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
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Why is electrical air insulation worse at high altitude?
At high altitude air is less dense.
This means that any ionised air molecules (or charged pollution particles) in the air have less other air molecules (or pollution particles) to collide with as these ionised/charged particles accelerate towards the electrical conductors they are attracted to (with the opposite electric potential) .
As they have a better chance at accelerating for longer without being slowed down by colliding with other air molecules/ pollution particles (as they would in more dense air) they are able to reach higher speeds on average and so can cause a Townsend avalanche more easily
A Townsend avalanche is where a charged particles impact causes more charged particles to be created and these accelerate and impact with other particles creating more charged particles, a kind of chain reaction.
Note: there is actually a knee point in this trend, where if the pressure is reduced too much there are not enough molecule's/particles close together so an avalanche breakdown of the air is less likely to occur.
FYI: This effect is related to Paschen's law
When there is almost no resistance in a circuit what is it called?
This is what is known as a "short circuit".
Why do you use air-core in a transformer?
Higher frequencies
the core can concentrate the magnetic lines of force
it takes time to magnetize and demagnetize iron
at about 10,000 hz we use powdered iron in some sort of glue (ferrite)
at somewhere around 1Mhz any magnetic material will no longer concentrate those magnetic flux lines
it will only get hot
so the core must be non magnetic (air is free)
open air conductors radiate heat all three ways:
conduction convection radiation
Does an open resistor measure 0 ohms?
No, an open resistor has a value of infinity. An open resistor typically will measure over 900 Megohms. A zero ohm resistor is exactly that, and will measure zero ohms. They are typically surface-mount devices.
What do they teach in electrical engineering courses?
Answer its all about electrical circuits and instruments. its applications in detail,workin of essential devices.It always goes hand in hand with electro-mechanical devices n such related stuff. It depends on the school you are applying to. so it'd be better if you take a look at the 'course plan'. It's available on-line for most schools and universities
Does motional emf call induced emf?
yes indused emf is also called motional emf.
If an open coil is subjected to a variable magnetic field, at the ends of the coil a potential difference is induced which is called induced emf.
If a coil is connected to an emf source and switched on, the rising current will produced an variable magnetic field which in turn produces an emf. It is called back emf.
Is Swinburne test applicable for dc series machine?
No.it is not applicable for dc series motor at no load..at no load armature current is too small in dc series motor and we know that speed is inversly proportional to the armature current(speed=v/kI-Ir/k).Hence speed is dangerously high which is not efficient for Swimburne's test...
Can a 9v dc motor produce 9v when it is used as an alternator?
A: No problem but don't expect the power to increase
This question is worded awkwardly, but, the answer would be, They must be of equal Voltage (primarily) and equal frequency. If they were of different voltages, one would feed the other. The amperages can be different.
If these generators were going into a distribution unit, the DU would have to have a frequency matcher, and would also force the output voltage to meet the load voltage (in the case of minor voltage deviations).
Can you rephrase this question into several smaller questions? I'll help you out as much as I can from there, and go to "MY Bio Page" and ask other more detailed questions.
What color are capacitors on a motherboard?
red (rare), metallic green, blue, light blue, brown, lime green, yellow, silver, black, gray, purple (rare).
What is the electric current voltage in Egypt?
220V single phase (domestic)
380V three phase (industrial)
A zener diode, a transistor, a rectifier diode, and a few resistors. A 10.5V zener diode will conduct until the voltage across it drops to below 10.5. If the relay is small enough, a zener diode is all you need. However, more than likely the current draw of the coil would burn the zener out. Use the zener to drive a transistor, and use the transistor to trigger the relay. V+ | |_______________________ | | _|_| _____|___ |/ \ 10.5V | | /___\ | 3 Relay | __|__ 3 Coil | / \ 3 0---------- /___\ 3 | | | 3 \ \ 4.7K | | / 2.2K / |____ ___| \ \ | / / | | | B | / C | |________|/ | |\ 2N2222 | | \ | | E |______________________| | _|_ \\\ When the voltage is above 10.5V the zener will conduct ant turn on the transistor. The transistor will power the relay. When the voltage drops below 10.5V the zener will stop conducting, shutting off the relay. The rectifier diode absorbs transients caused by the field breakdown in the coil, protecting the transistor. Just a plain resistor will do it or you may follows suggestion and use a computer to do that. The last time i used those ancient devices i find out they operate as a current device like minimum pull in current source. So a passive resistor in series will insure the minimum pull in source however it could be higher then the 10.5 v you need.The above designi just plain silly.
How do you change the hall effect switch in a 93 cadillac deville 4.9L?
It is magnetic pick-up in the bottom of distributor. If car has alot of miles on engine, best to get a rebuilt distibutor. Otherwise, use a technition to replace pick-up. Have to disassmble distibutor to access pick-up.
A parallel circuit is one which the current passes through the electrical devices in separate paths.
For example, consider 2 resistors (loads):
- If the current must pass through one resistor to get to the other one, then it is a series circuit.
- If the current path splits so that the current can pass through each resistor independently, then it is a parallel circuit.
A practical example
In a house each lamp and its light switch are wired in series with each other but all the separate circuits feeding the lights in a house are wired in parallel with each other because any one light can be either on or off independently of the others.
if one light burns out the others wll still light
A parallel circuit is one in which two or more circuit elements are connected in parallel, for example, two light switches wired so that either switch will turn on the light, or two bulbs wired together so that one swirch turns them both on. More info: http://www.allaboutcircuits.com/vol_1/chpt_5/1.html
What are "series" and "parallel" circuits?
a parallel circut is when their are items parallel to eachother. like for example making a simple electrical circut.
a parallel circuit is when electricity flows through more than one pathway
What is the voltage drop running through the parallel potion of the circuit?
A: There is no voltage drop running through in a parallel circuit but rather the voltage drop across each branch of a parallel circuit is the same
What is the difference between single phase circuit and tree phase circuit?
A single-phase circuit has one live conductor and one neutral conductor, typically used for residential applications. A three-phase circuit has three live conductors and one neutral conductor, used for higher power industrial applications due to its ability to provide a more balanced power distribution.
What is operation of an antihunting relay in circuit breaker?
This is also called anti pumping relay. for understanding you have to understand the working of breaker. positive extends to "Low Pressure Lockout" & "Low Pressure Alarm". after maintain the pressure in breaker these NO becomes NC and when breaker closes the auxiliary of breaker get closed and simultaneously extend the positive to the antipumping relay coil by auxiliary contact. by this coil get energised and holding contact get connected and the one of the contact of antipumping coil (NC) become NO which disconnect the command supply of main breaker. by this till when the antipumping relay get energised no further command (+ve) extends to breaker closing coil. This is Antipumping/ Antihunting Relay.
What is difference between servo and VFD?
A servo system is a closed-loop motion control system usually consisting of a motor (servo motor) usually a synchronous motor combined with an encoder for position/speed feedback, and a drive (servo drive) which is the electronic amplifier. A servo drive usually has some advanced functionality, like PLCopen commands, custom accel/decel ramps, compensation, and provides an interface for synchronization with the control system and other drives. A servo is a VFD, in that it probably uses triacs to control the output waveform that drives the motor; by varying the frequency and magnitude, it can precisely control the motor with closed-loop feedback of position/velocity from the encoder.
A VFD (Variable Frequency Drive, also known as a Variable Frequency Inverter) generally refers to the electronic amplifier of an open-loop system, which can vary the frequency and magnitude to control speed. Without closed-loop control it will not be as precise as a servo system, but is usually good enough for most applications and will probably provide soft-start functionality and other protections to the motor.
See also What_is_the_difference_between_servo_drive_and_variable_frequency_drive
How do you set motor amp overload?
There are many types of overload protection these days and all are based on the FLA (full load amps) of the motor.
If 5 miliamps were flowing through a 1-k ohm what would ther power consumption be?
Power = I^2*R, so P = (5 x 10^-3)^2*(1,000) = 25mW
What is the difference between 100ohm and 100E?
It is the same, you can use ohm, µ, R or E to represent Ohm, like 2E2 or 2R2 = 2.2 Ohm and 2K2 = 2.2 Kilo Ohm also 2M2 will be 2.2 Mega Ohm.
If a negative current enters a negative voltage will it be negative or positive?
A current is never concidered negative. The current will always flow from a higher voltage to a lower.
For example:
12 -> 0V as 12V is a higher potential than 0V. The current is measured in Ampere.
0V -> -12V as 0V is a higher potential than -12V. The current is measured in Ampere. Not negative Ampere despite the fact that it floats from the 0V potential
AnswerThe term 'negative', in the sense of 'polarity', doesn't apply to either current or voltage (potential difference), although it does apply to potential -so, the previous answer should read that current 'flows from a higher potential to a lower potential', not 'from a higher voltage to a lower voltage'.
However, we do use the terms 'negative' and 'positive' in the sense of 'sense' or 'direction'. So, when we talk about a 'negative voltage', what we mean is a voltage that is acting in the opposite direction to another voltage -for example, if we consider the direction in which a battery's voltage (E) to be acting to be 'positive', then any resulting voltage drop (V) will be acting in the 'negative' direction -i.e. E - V = 0 (i.e. the algebraic sum of the voltages around that circuit is zero).
In the same way, we can describe current as being 'positive' or 'negative' in the sense of its direction. For example, if one current (I1) is approaching a junction, and two currents (I2 and I3) are leaving that junction, we can write: I1 - I2 - I3 = 0 (i.e. the algebraic sum of the currents at that junction is zero).
Unfortunately, this doesn't specifically answer your question which, unfortunately, is rather confusing and needs to be rephrased.
