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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 is reverse power in generator and what happens in couse of reverse power?
Not necessarily. Reverse power simply means that the load is providing power to the generator, instead of the reverse. Its not a good place to be, because you waste the power needed to turn the generator, and you could damage it as well.
What is the difference between local oscillator and oscillator?
Oscillator is a generic word for any circuit that produces an alternative signal.
The shape of the signal, its stability and its output impedance are not considered in this case.
"Local oscillator" is one specific type of oscillator used in radio receiver for the purpose of frequency conversion. the input Radio Frequency( RF ) signal is "mixed" with the local oscillator signal and the subtraction of two frequencies is obtained at the output.
"Mixing" in this context means: "multiplication"\
In some other context in electronics (specially audio) mixing means "adding"
the mathematical operation for local oscillator is F out=Fin - F loc.osc.
The output of the mixing operation can also be Fin+F loc.Osc. But this higher frequency is usually filtered out.
The local oscillator needs to be a pure sine wave with a very good frequency stability and usually very stable output voltage.
Recently very good "synthesizers" are introduced in the market that permit generation "programmable local oscillation"
Oscillators are used in a lot of applications. The fact that they oscillate, meaning switch between a zero and positive orbetween a negative-positive value in a repetitive way, makes them useful as a time base.
As time base, they can be used to activate processes that are time-dependent, eg. a computer: has an internal clock (several, to be more corect) that is driven by a kind af an oscillator.
Most of these oscillators to drive time-based electronics are digital, meaning the oscillation is a square wave between 0volts and some positive value (eg. 3.3V or 5V)
Another common use of oscillators is for data communication: a waveform of a certain frequency is generated by an oscillator, and information is superponed on this electromagnetic wave.
Other appliances that use waves generated by oscillators are like microwave ovens, radar, sybthesizer, clock radio, modem (both digital and analog types), sirens, Christmas lights, ...
You can be sure, if it has anything complicated electronic in it, it almost certainly has an oscillator build in.
see also http://en.wikipedia.org/wiki/Oscillation
When measuring with an ammeter the ammeter must be connected in?
When measuring a load current, an ammeter is connected in series with the load. The exception is for a clamp on style AC ammeter, which is clamped around one of the conductors, making its measurements as a transformer.
Can you replace 2200 uf 24 volt capacitor with a 2200 uf 16 volt capacitor?
NO dont do it if you devalue a capacitors voltage parameter what will it do when it is face to face with 20V ? The voltage will destroy the thing. Remember it is OK for you to use a higher voltage parameter for a capacitor but never lower
It is a usually square or rectangle set of bars that hold many lights for tv sets or homes or anything that needs a lot of lights.
What type of motor has a stator?
An electric motor has a stator and a rotor.
The stator does not move.
The rotor rotates inside the stator.
In a 3 phase 480 panel what voltage should you get phase to phase?
The voltage you are referring to is a 'line-to-line' voltage ('line voltage'), as there is no such thing as a 'phase-to-phase' voltage.
480 volts. In real life, the voltage will vary slightly by up to 3% (14 V) on a properly sized circuit. Line to neutral will measure 277 volts, plus or minus 3%.
Measures current by magnetic field induced into the clamp. You need to clamp a single conductor. For example you couldn't just clamp a lamp cord since it has two conductors and the current is going in opposite directions and the fields cancel each other out.
Can all dc motors be speed controlled?
A: YES it will however the most reasonable solution would be to keep frequency fix and change the duty cycle
Does digital voltmeter measures rms voltage or peak to peak voltage or average?
Yes, most DMM are ''average responding", giving accurate rms reading if the ac voltage signal is a pure sine wave. They measure the average of the absolute value of ac voltage and are calibrated so that reading are corrected to that of the rms value of a sine wave.Error occur if harmonic are present.
Is a force of friction a vector or scaler quantity?
Either, or both. Motion can be described in either vector or scalar terms. Speed is a scalar quantity, having only a magnitude. Velocity is a vector quantity, having both magnitude and direction. Acceleration is a vector quantity.
What would be the size of Cable for a 40 kw 3 phase oven?
It is not possible to answer the question without knowing the supply voltage. Conductors (wires) are sized according to current (amps), not KW. Amps = watts / volts As you can see, there is no way to determine amps (needed to size the wire), without knowing both the KW and the voltage. If this is on a test, it is a trick question. If you are really trying to size a cable for a real stove, hire a licensed electrician! Improperly sized wire can start a fire.
The voltage and current sine waves cross the zero line at the same time and going in the same direction. The phase angle is 0°. They are said to be in-phase.
How many people can ride on maglev train?
A small, three car maglev train weighs more or less 100 tons, so they are relatively light trains.
What is the difference between power transistor and power mosfet?
A BJT is one type of transistor and POWER TRANSISTOR can be BJT or MOSFET or some other phenomena.POWER TRANSISTOR are usually those who are used at high current ratings e.g at POWER AMPLIFIER where large transistors are used at final stage to gain output.
What happens when you increase the current to a solenoid?
increasing the voltage increases the current. this is because when you increase the voltage you make the pressure that is pushing on the current (which is making it move) greater, therefore increasing it.
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Ohms law states that, the current is directly proportional to the applied (EMF) voltage and inversely proportional to the resistance in a circuit.
The formula you are looking for is I = E/R. You supply some figures for Voltage (E) and Resistance (R).
What is the formula for electric power?
the formulas for calculating electrical energy is
E (dissipated in a resistor R)=(I^2)*R*t=VI=(V^2)/R
where V is voltage across resistor ,I is current,t is time.
or if there is a function of time the equation becomes
E= integral from 0 to t (i(t)^2*R) dt
it is the integral of the power dissipated for the time in question.
Why you transfer voltage is 11kv33kv66kv?
All sinusoidal AC voltages are multiples of 1.1. This is due to the form factor, which is the ratio of the quadratic mean value of the voltage with the average voltage, which is pi/2√2=1.1 (approximately). It also provides the most economic means of constructing step up/down transformers.
AnswerIn the UK, 33 kV (along with 66 kV) is considered to be a primary distribution voltage level, whereas 11 kV is secondary distribution voltage level. Incidentally, the correct symbol for 'kilovolt' is 'kV', not 'kv'.
What is the Current carrying capacity of 35 sq mm 4 core aluminium cable?
Your question doesn't make any sense. Do you mean 630 mm2, in which case the fact that the conductor is square is irrelevant. Or do you mean a square with 630-mm sides, in which case it is enormous!
What is produced first current or voltage?
current flows as a result of potential difference i.e. in a circuit if there is no voltage difference between two points, no current can flow between those two points. So voltage has to be produced first.
How many amps does a 2 hp 240 volt single phase motor draw?
One horsepower electric is defined as 746 watts, so two horsepower is 1492 watts. Divide that by 240 volts, and you get about 6.2 amperes. Now you have to consider the power factor, which is the ratio of apparent power to true power, caused by the inductive (reactive) load of the motor causing the current to be out of phase with respect to voltage. You did not say what the power factor was, so lets assume it is 0.8. That makes the current about 7.75 amperes.
That's running current, at full load. Starting current is often four times higher. The NEC list this motor has drawing 12 amps and to wire this motor you would use this value, unless the actual nameplate amps on the motor was higher.
One volt is the electric potential required to generate one ampere through one ohm.
One volt is the electric potential involved when one ampere generates one watt of power.
One volt is one joule per coulomb.
How do electrical contactors work?
A contactor is an electrically controlled switch (relay) used for switching a power circuit. an electro pneumatic contactor is similar to the above except it uses a pneumatic signal to initiate the switching of the electric power circuit. an electro magnetic contactor is a contactor driven by an electric control signal. It us usually just called a contactor.
