Electrical Engineering

CAPACITOR

Explanation:

An interesting property of capacitors is that they will block DC after they become charged, but will (for the most part) allow AC to flow through. When a capacitor is fully discharged, DC can flow through it freely, but as it is doing so, the cap is gradually becoming charged. Finally, when it has reached its storage limit, the cap will not allow any more electricity to flow through it, and will act as a blocker on the circuit. This can be observed if you simply wire a capacitor in series with a simple circuit connecting a battery to a light. When the circuit first comes on, the light will turn on, but after some time (when the cap becomes fully charged) it will turn off. Exactly how long it takes this to happen depends on the capacitance of the cap; With very low-capacitance caps, it will probably happen faster than your eye can perceive, but it still will happen. If you remove the battery and simply leave the cap connected to the light, the light will turn on again as the cap flows into itself, acting like a battery, and the light will stay on until the cap fully discharges. So a cap blocks DC; If you think about it for a moment, you should be able to understand why they allow AC to pass through: AC keeps reversing its polarity. As long as the AC switches fast enough to prevent the cap from becoming fully charged in any direction, then the cap will partially charge in one direction, and as the AC polarity reverses, the cap will start to discharge, then charge in the opposite direction. Very low-capacitance caps may partially block the AC because they become fully loaded before the AC cycle is complete, however. TOO many words for an explanation yes it block DC and it acts as a storage of energy. charged or not charged it will block dc IF THE DC changes then more or less it will pass this levels because varying DC is AC after all,

In a perfect inductor (one with no series internal resistance), the current lags the voltage by 90 degrees. If the inductor has series internal resistance, then the current will lag the voltage by less than 90 degrees - the more the resistance in series with the inductor, the smaller the angle. The tangent of the angle can be found from the ratio of the inductive reactance of the inductor to the DC resistance of the inductor.

That is, Tan (phase angle) = (2 x pi x frequency (Hz) x inductance (H)) divided by resistance (ohms)

eg, a 1 henry, 100 ohm inductor on 60Hz would give:

(2 x pi x 60 x 1) / 100 = 3.77; tan-1(3.77) gives 75 degrees lag of current behind voltage.

The cosine of this angle gives the 'power factor' for the inductor - that is, the amount of useful energy dissipated in the inductor. Cos 75 is about 0.25 - so 25% of the energy actually does useful work (heat) - the rest of the energy (75%) is returned to the supply mains when the inductor discharges its magnetic field.

Without going into the math, the change in speed increases the torque the motor can supply. The further the motor speed and supply speed are apart (known as the slip), the greater the torque will be.

It depends on the device, if for instances the machine is a pc, laptop mobile phone charger or anything that has a modern switch mode power supply built into it then you can use it on anything between 110 and 240, it will auto select, i don't recommend attaching a machine that is rated at 240v to a 460v supply, you will need to contact the manufacture to determine operating parameter's.

a circuit breaker trips on overload,if this breaker has tripped many times it may be worn out,if there is a overload happening the breaker is doing it s job keeping you safe.Main breaker needs to be replaced when your meter has been pulled(removed from metersocket)Have a electrician look at it and verify problem, you should not attempt to change out yourself it will be live.......

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It would probably spin, but I don't know if it'd last very long.

First, the speed of AC motors typically are dependent on the frequency ( 50 Hz or 60 Hz) so the motor would be trying to spin 20% faster than designed.

Also, because of the higher voltage, you would have more current running through the motor windings (wiring) than designed. These 2 conditions would cause overheating of the bearings as well as the wiring inside the motor.

hi...

to determine the high fault current when the short circuit done at the output terminal of the generator...

more information check any book of power element analysis and chapter (three phase fault at unloaded generator)...

with my Greetings

well how big is the candle? which material is it made out, and how long does the candle burn?

The automatic door has a special infrared sensor in which a person walks towards the door then the sensor detects that someone in there, it then activates the electromagnets in the entrance system which allows the door to open at at certain speed.

Generally for export only transformer, generator side is connected in delta and load side is connected in star. For export import transformers star star connection may be preferred by some since this avoids a grounding transformer on generator side and perhaps save on neutral insulation. I am not sure how correct this practice is but so many systems are running in this configuration. Perhaps it may be felt to be less harmful than operating delta system incorrectly. Yd or Dy connection is standard for all unit connected generators.

The main reasons for connecting generator side winding in delta are:

1) To facilitate grounding of generator system with higher impedance and the load system with lower impedance.

2)To break The zero sequence circuit for the system at the transformer. This ensures the load side zero sequence currents do not come to the generator system.

3) III rd and similar harmonics will circulate in delta and will not come to generator system.

The trafo vector group will be Dy if load voltage is lower and Yd if load side voltage is higher.

Dy1,5,7 or 11 selection depends on requirement for load synchronizing ,standardizing or ready trafo availability. All vector groups are functionally similar.

Wouldn't this depend on the voltage of the system? Like if it is a 460 or 208v system it would be 208 or 460v. There should be 3 lines L1 L2 and L3 all measure the input voltage. The wye or star point voltage on a three phase system is the square root of three. This number (1.73) is divided into the three phase voltage to get the voltage to neutral (ground). 208/1.73 = 120 volts, 415/1.73 = 240 volts, 480/1.73 = 277 volts, 600/1.73 = 347 volts.

Using Ohms law ... E = I * R

Where

E is electromotive force in volts

R is resistance in Ohms

I is the current in amps (why "I", I don't know maybe some one else can edit this line)

E = 2 amps * 10 ohms = 20 volts

It is number 4 copper wire that is generally equivalent to number 2 aluminum wire as regards its ability to handle current. Voltage is not an issue with the conductor but, rather, with the insulation. The length of the run is immaterial ifthe original wire size for aluminum was correctly specified for the application. Think this through and it should make sense. Note that if you are considering an upgrade from aluminum to copper, you would be wise to do just a bit more research. Freelancing in electrical work without knowing all the facts can result in property damage from fire. Death is also a possibility, either from the effects of the fire, should one occur, or from electric shock. These eventualities can result from even the most simple mistakes in a job like this. Do all your homework before proceeding, and talk to at least two electrical contractors before strapping on your tool belt. Show everyone how smart you are and hire the job out to a qualified professional if you even think you have any doubts about what is involved in the undertaking.

This is because the current kills the magnetized/domain particles and so it becomes un-magnetized.

When the domains are magnetized they all face the direction of the magnet but when they have been destroyed by an AC current... they are pretty much jumbled together!

It isn't necessarily so. The capacitive voltage is the product of the current and capacitive reactance, while the inductive voltage is the product of the current and the inductive reactance. So it depends whether the capacitive reactance is greater or smaller than the inductive reactance!

Kilo simply means 1000. Volt-ampere (VA) is a measure of power, similar to the watt. Volt is a measure of voltage, or electrical pressure. Voltage means electricity is available, but unless it is actually used, no current (amperes) flows, and no work (power) is done. Suppose you have a motor that needs 1000 volts to run, and when it is on it draws one ampere (amp) of current. We would say the motor supply voltage is one kilovolt. When the motor is running, we would say it uses one kilovolt-ampere (1KVA) of power (1 ampere * 1000 volts = 1000 VA or 1 KVA).

Inductance

You can easily create an induction loop by getting some good quality wire, and twisting it around into a loop (i.e. a "2 turns series"). This can be used to improve the signal on your radio or television.

BS7671:2008 Requirements for Electrical Installations: IEE Wiring Regulations, 17th Edition. Strictly speaking, this document is published by the IET -the Institution of Engineering and Technology, as the IEE (Institution of Electrical Engineers) no longer exists.

200 and 100

10 volts divided by 30 ohms is 0.33333 amperes.

10 volts times 0.33333 amperes is 3.3333 watts.

Note: Resistance is dependent on temperature. 3 watts is enough power to raise the temperature enough to affect the resistance, changing the results.