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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 metal is normally used for wires in electric circuits?
Gold or silicon may be the metal most popular for use in electronic circuits. Gold because it does not corrode in the atmosphere and silicon because it is used to make semi-conductors.
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A lot of gold is used for fine wires and contacts... Silver and copper quickly oxidise (also called "tarnish") if exposed to the atmosphere so are not used as much despite their very good conductivity which is almost as good as gold.
A capacitor is a device used in most electronic devices to store electric charge in order to keep the system functioning. If for example a television was in used for a few hours and then shot down, if aTechnical has to perform some hardware services on the device due to some malfunctions, He needs to handle the capacitor with care or have it discharged before touching it with his bare hands, otherwise he stands the risk of electric shock and consequently death.
How can a 240V single phase split ac work in the US which has a 120V 2 phase system?
Note
"2-phase" to describe US residential service is depricated nomenclature. US residential service is single phase because the two hot supply phases have 0 degrees of separation between their phases: therefore they are in phase.
The two phases are pulled from 2 out of 3 corners on a 240v (line-to-line) 3-phase delta-primary transformer, usually out in the street. (Sometimes at your house if it's a big one). Basically all power is generated and transmitted as 3-phase. Usually around 415V 3-phase comes into the primary of the 3-phase transformer. (It could be delta- or wye-connected.) The secondary windings for all three phases will each have a center-tapped connection, and that's grounded at the panel. This is the neutral wire. All circuits in houses return via the "common" or "neutral" wire to this point, which happens to be grounded at the panel. Note: no neutral wires should be grounded anywhere else. The two "corners" are 240v relative to each other, and 120v each to the center tap. Each 240V circuit really is two hot wires plus a neutral, which is why it's often wrongly called two-phase when in fact it's just single-phase. For each 120V circuit in the house you're going to use one hot wire and one neutral wire. The neutral wire provides a return path for currents back to the generating station. In some installations, such as apartment blocks, the third leg of power would be at 208V with respect to the center tap.
Another answer
Just what does "220v single-phase split ac in the US which has a 110v 2-phase system" mean?
The vast majority of electricity in the US is delivered as single phase or three phase. The only areas in the US that use 2-phase [for industrial and commercial purposes] are Philadelphia/South Jersey [where it is being phased out-no joke intended] and somewhere out west...
It was one of the early poly-phase options pursued because of the natural magnetic differential between phases [makes motors spin without a capacitor]
Most residences receive 220-240 volt single phase electricity with a grounded center-tapped neutral, the purpose being to limit voltage to ground to less than 150 volts from either "hot".
If you can Chang winding 50hz to 60hz?
If you have the motor rewound you could possibly have it changed. You can run some 50 hz motors on a 60 hz system but there are no guarantees. The motor will run faster and there is a chance it will overheat. There is no way to change the field connections of a motor to accomplish this. Best bet is to just purchase the correct motor.
Can you connect a 3 phase motor to a 1 phase supply?
Single phase to three phase
The physical internal windings between single phase and three phase motors makes this an impossibility That being said money can make anything happen. Depending on the amount of money you want to spend to make this happen there is a device on the market called a VFD ( Variable Frequency Drive). On the three phase input terminals you apply your single phase voltage. On the output terminals you connect your three phase motor. When run in this configuration there is an internal switch that has to be changed to let the VFD know that it should be looking for only two lines on the input to be hot. Other wise the VFD thinks that there is a line loss on the three phase input terminals and the unit will not start.
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Some 3 phase motor speed controllers can be run off a single phase supply, this caused us a problem at work when a new speed control was fitted to some laundry equipment, as we then had to rewire the supply to bring in a nuetral, so i suggest a speed controller is probably the solution.
What are universal motor brushes made of?
the brush is a peice of carbon that is attached to the startor by a brush holder.
What can high voltage do to you?
The really dangerous thing is how many electrons per second travel in the human body and this is the current. So the current is the "dangerous" part, and, as i remember correctly,
if you stick(similar to electrolysis where your blood acts as an electrolyte ,here current is directly set up in the electrolyte) 2 electrode needles in your body, a 9V battery is sufficient to electrocute you (because the resistance of the electrolyte in the blood is really low and so the current is high), but if you don't stick(just touching the too needles with hand etc etc..) anything in your body but only touch two wires, the tissue resistance is high enough and the 9V battery is harmless.
Do Power is directly proportional to resistance or inversely proportional to resistance?
It is both proportional and inversely propertional to resistance however I am not exactly sure why which is why I am searching Google ATM for answers.
The formula to use is, phase voltage /1.73 = phase to neutral (ground) voltage.
CommentThere is no such thing as a 'phase to phase', or 'phase to neutral' voltage. The correct terms are 'line to line' and 'line to neutral'. So the above answer should read: line voltage/1.73= line to neutral voltage = phase voltage.
How does on load tap changers operate?
On-load tap-changers are operated by an electric motor, often by driving a flywheel mechanism. The operation of the tap-changer is controlled by an AVR (automatic voltage regulator) which monitors the transformer's secondary voltage.
Induction heating is the process of heating an electrically conducting object (usually a metal) by electromagnetic induction, where eddy currents are generated within the metal and resistance leads to Joule heating of the metal.induction heater including high frequency induction heating machine and middle frequencey heating machine.
Induction heating applications for an induction furnace include induction welding, induction brazing, induction hardening, induction melting, quenching, forging, soldening, induction annealing and other forms of heat treatment.
Induction heating is often used to heat graphite crucibles (containing other materials) and is used extensively in the semiconductor industry for the heating of silicon and other semiconductors.
Induction heating can produce high power densities which allow short interaction times to reach the required temperature. That translates into lots of energy transferred into a material right now, with a very rapid rise in temperature.
A megger test is done to check the insulation factor of wires or devices. This is to make sure that when the working voltage is applied, a short circuit to ground will not occur due to a problem with the insulation of the device or wire.
Does a induction motor need excitation?
The induction motor is the special kind of motor which runs below and above the synchronous speed. which the synchronous motor runs nearly equal the synchronous speed. The operation of synchronous motor runs with dc field excited hence separate dc field current is given to the field circuit. where as the induction motor the field and main field is drawn from the same supply hence no excitation is required. But due to this separate starting mechanism has to be required in case of the single phase induction motor.
Is static electricity an excess of neutrons?
Static electricity is not an excess of atoms, but rather differences in the charges of those atoms. Static electricity happens when there is a separation of positive and negative charges caused by electrons moving from one material to another.
Ohm's Law
What is the resistance of 70ohms and 30 ohms in a parallel circuit?
we have this 1/Re = (1/R1)+(1/R2) for calculating the effective resistance when resistances are connected in parallel
so the answer would be Re =( 70*30) / (70+ 30)
= 21 ohms
What is the working principle of a spygmomanometer?
The sphygmomanometer is designed to monitor blood pressure by measuring the force of the blood in the heart where the pressure is greatest. This occurs during the contraction of the ventricles, when blood is pumped from the heart to the rest of the body (systolic pressure). The minimal force is also measured. This occurs during the period when the heart is relaxed between beats and pressure is lowest (diastolic pressure).
How do you convert hertz into volts?
'Hertz' is the modern name for 'cycles per second' and represents how many times an alternating current (AC) changes from + to - per second and has nothing to do with voltage that can be either AC or DC. Tus if you have an alternator and can rotate the shaft 60 times per second with a voltage of 120 volts you will produce the same AC voltage that you find in your wall outlet (Alternators produce AC while generators produce DC electricity.
What do you mean by Polarity of a transformer?
Transformer polarity is the direction the secondary goes relative to the primary, or relative to another secondary. Usually, polarity does not matter, for example in the case where the secondary is connected to a rectifier / filter / regulator. Sometimes, it does matter, particularly if there are two secondaries used to provide DC isolation between a preamp and a final amplifier in push-pull configuration. It can also matter if the overall circuit is involved in a feedback loop and phase inversion is a factor.
Answer
When applied to transformers, the term 'polarity' describes the direction in which the secondary voltage is acting relative to the direction of the primary voltage. Polarity is determined by the directions in which the primary and secondary windings are wound relative to each other.
Polarity is described as being either 'additive' or 'subtractive', and can be determined by of connecting one pair of primary and secondary terminals together. If the voltage measured between the other adjacent primary and secondary terminals is greater than the primary voltage, then the transformer has 'additive' polarity; if the voltage is less than the primary voltage, then the transformer has 'subtractive' polarity.
Knowing the polarity of individual transformers is important when two single-phase transformers are connected in parallel with each other because, if polarity is ignored, then an incorrect connection might result, causing a large circulating current through the two secondary windings.
Where would you find a forward and reverse wiring diagram?
Are you asking about a wiring diagram for the right switches to make an electric motor turn either in a forward or a reverse direction? Or for a linear motor to go either one way or the other?
If so, please ask your question again and state what typeof electric motor you are asking about, because the direction-switching circuit needed will depend on the type of motor.
Some types of motors are not reversible at all.
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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.
Does the current in a pure capacitive circuit lead or lag the applied voltage?
Just remember our friend ELI the ICE man!
E is voltage, I is current, L is inductance, and C is capacitance.
ELI
In an inductively reactive circuit (L), the voltage (E) comes first, then the current (I) lags behind.
ICE
In a capacitively reactive circuit (C), the current (I) leads, then the voltage (E) comes later.
Note that while your assumption (in the stated question) is correct, an engineer or electrician would not say it that way. The voltage waveform is the constant, and the current waveform is said to lead or lag. This is because reactive or non-linear loads distort the current. If you look at a power-factor meter, and it says leading or lagging, it is referring to the current. It would be more accurate to re-phrase your question: In a capacitive reactive circuit does the current lead the voltage? Yes!
Answer #2:
Another method I learned from one of my EE professor is that in an inductor the current lags the voltage because the electrons get dizzy going through all of those loops (coils) in the inductor and "lag" behind the voltage.
Overall brightness (not individual bulbs' brightness) will increase when we connect them in parallel & it will decrease when we connect them in series.
High voltage transmission and distribution lines utilise three-phase electricity. There are two commonly-used connections used in this system, termed a 'delta' and a 'star' (or 'wye') connection. A delta connection provides three energised conductors, termed 'line conductors', while a star connection provides three energised conductors ('line conductors') together with a neutral conductor. However, in the case of a star connection, provided the load is balanced, no current flows through the neutral conductor. In the case of high-voltage transmission and distribution lines, their loads are very close to being balanced, so there is no need to provide a neutral in the case of a star-connected system, as any slight imbalance can be compensated for in slightly different line currents.
Why do people say 110 volts instead of 120 volts?
Europe uses 220/240 volts, USA and Canada use 110/120 volts. The lower voltage is less dangerous if you touch a live wire.
