0
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 amplitude demodulator?
(I am assuming you want to know what an "AM Demodulator" is, as follows) AM stands for Amplitude Modulation, perhaps the most basic kind of modulation of a radio carrier wave. Information, typically voice or music, is impressed on a radio carrier by simply varying the strength or 'amplitude' of the carrier (which is ordinarily at a much higher frequency than the information signal) versus time. An AM Demodulator, then, is a device which recovers the original signal, that is the voice or music, from the modulated carrier wave after it has been transmitted from the source to the receiver (which typically filters and amplifies the received signal before it is applied to the demodulator). The simplest AM Demodulator is a simple "diode", a 2 terminal semiconductor (or vacuum tube) device which, together with another filter, can convert the AM modulated carrier directly into the original form, discarding the carrier wave in the process. This is known as an "Envelope Detector". Other types of AM Demodulators exist, principally the "Product Detector". See the subtopic "AM Radio" in the Wikipedia entry for "Demodulation" for a little more information (it's not overly technical).
An uncharged capacitor acts like a short circuit when voltage is first applied to it?
Yes it does. Capacitors and capacitor banks have a high inrush current when first energized. As an example this is the reason that VFD's place a resistor in series with the capacitors for a short period of time when they are first energized to prevent damage to the rectification componente. They call it a precharge circuit. Current leads voltage by 90 deg in a purely capacitive circuit.
How many circuits can you have with 100A service?
As many as you want without exceeding the 100amps. You could have 100 circuits if all you have is a single 100watt light on each circuit.
What is the difference in the lower end of a 1982 GM motor and a 1996 GM motor?
1 piece rear main seal and the mounting location for the fuel pump is blocked off. May have bosses cast in lifter vally for hydrolic roller cam on the newer block
Is your ignition wire hooked up to your distributor? 1.This small pink wire hooks into the top left part of the distributor marked "BAT" Is your battery fully charged? Is your starter wired up correctly? 1.The 2 skinny red wires and the + battery cable wire go to the big terminal on the starter. 2.The skinny purple wire goes to the small "S" terminal on the starter. Make sure the - battery cable is grounded correctly.Hope this helps you.
What will happen if instrument with 110v supply voltage give 220 v supply?
the appliance will burn out, eg if it is a 60 watt light bulb it will burn at 120 watt for as long as the fillament can take it and that wont be long
The 80% ideal is from the NEC. Let's say you have a standard 15A circuit. This circuit is rated to carry a maximum of 15A, no more. If you try to draw more than 15A, the breaker will pop. Now, you can put 15A worth of appliances on this circuit, but then you are running it at its maximum all the time. If you add anything else to this circuit, you will pop the breaker. If you have something that draws surge current, it can opo the breaker under normal use. You have no "wiggle room" when you load it at its maximum. Also, as touched on above, if you run your circuit at the maximum you cannot add anything else. This is generally a sign that you need to upgrade your wiring. Furthermore, the breaker can handle 15A indefinitly under standard test conditions, which are close to ideal. Your breaker box may not be ideal. Breakers are thermal devices, so self heating and heating from other breakers can be a problem. If your breaker is hot, it will pop sooner than if it is cold. The more current that flows through it, the hotter it will get. If you are overloading circuits the easiest thing to do is to break the circuit up into multiple circuits. The exact implementation will depend on the situation.
Explain construction and working of a Solar Cell?
How A Photovoltic Cell Works ----
Return Photovoltaics
The "photovoltaic effect" is the basic physical process through which a PV cell converts sunlight into electricity. Sunlight is composed of photons, or particles of solar energy. These photons contain various amounts of energy corresponding to the different wavelengths of the solar spectrum. When photons strike a PV cell, they may be reflected or absorbed, or they may pass right through. Only the absorbed photons generate electricity. When this happens, the energy of the photon is transferred to an electron in an atom of the cell (which is actually a semiconductor). With its newfound energy, the electron is able to escape from its normal position associated with that atom to become part of the current in an electrical circuit. By leaving this position, the electron causes a "hole" to form. Special electrical properties of the PV cell-a built-in electric field-provide the voltage needed to drive the current through an external load (such as a light bulb).
p-Types, n-Types, and the Electric Field
To induce the electric field within a PV cell, two separate semiconductors are sandwiched together. The "p" and "n" types of semiconductors correspond to "positive" and "negative" because of their abundance of holes or electrons (the extra electrons make an "n" type because an electron actually has a negative charge). Although both materials are electrically neutral, n-type silicon has excess electrons and p-type silicon has excess holes. Sandwiching these together creates a p/n junction at their interface, thereby creating an electric field. When the p-type and n-type semiconductors are sandwiched together, the excess electrons in the n-type material flow to the p-type, and the holes thereby vacated during this process flow to the n-type. (The concept of a hole moving is somewhat like looking at a bubble in a liquid. Although it's the liquid that is actually moving, it's easier to describe the motion of the bubble as it moves in the opposite direction.) Through this electron and hole flow, the two semiconductors act as a battery, creating an electric field at the surface where they meet (known as the "junction"). It's this field that causes the electrons to jump from the semiconductor out toward the surface and make them available for the electrical circuit. At this same time, the holes move in the opposite direction, toward the positive surface, where they await incoming electrons. Making n and p Material The most common way of making p-type or n-type silicon material is to add an element that has an extra electron or is lacking an electron. In silicon, we use a process called "doping." We'll use silicon as an example because crystalline silicon was the semiconductor material used in the earliest successful PV devices, it's still the most widely used PV material, and, although other PV materials and designs exploit the PV effect in slightly different ways, knowing how the effect works in crystalline silicon gives us a basic understanding of how it works in all devices. Absorption and Conduction In a PV cell, photons are absorbed in the p layer. It's very important to "tune" this layer to the properties of the incoming photons to absorb as many as possible and thereby free as many electrons as possible. Another challenge is to keep the electrons from meeting up with holes and "recombining" with them before they can escape the cell. To do this, we design the material so that the electrons are freed as close to the junction as possible, so that the electric field can help send them through the "conduction" layer (the n layer) and out into the electric circuit. By maximizing all these characteristics, we improve the conversion efficiency* of the PV cell.
To make an efficient solar cell, we try to maximize absorption, minimize reflection and recombination, and thereby maximize conduction. *The conversion efficiency of a PV cell is the proportion of sunlight energy that the cell converts to electrical energy. This is very important when discussing PV devices, because improving this efficiency is vital to making PV energy competitive with more traditional sources of energy (e.g., fossil fuels). Naturally, if one efficient solar panel can provide as much energy as two less-efficient panels, then the cost of that energy (not to mention the space required) will be reduced. For comparison, the earliest PV devices converted about 1%-2% of sunlight energy into electric energy. Today's PV devices convert 7%-17% of light energy into electric energy. Of course, the other side of the equation is the money it costs to manufacture the PV devices. This has been improved over the years as well. In fact, today's PV systems produce electricity at a fraction of the cost of early PV systems.
What is the formula for transient spike computation in an inductive load?
E=I x R. The inductive spike occurs as the circuit is opened. The collapsing magnetic field causes the inductor to become the source of the circuit. For example consider a circuit consisting of a 10 volt battery, a 10 mh inductor, and a 10 ohm resistor all in series. With the switch closed, 1 amp will flow through the circuit (after 5 mS). The 5 mS is the time it takes the current to rise from 0 to 1 amp. This is given by the formual TC=L/R where TC is the time constant in seconds, L is the inductance in henries, and R is the resistance in ohms. It takes 5 time constants for the current to reach the maximum current which is determined by I=E/R (Ohm's Law). The delay is caused by the counter EMF generated in the coil as flux lines cut through adjacent turns of the inductor. After 5 time constants, the current is at 1 amp. When we open the switch, it will take 5 time constants for the current to drop to 0 amps. However, this will not be 5 mS because the resistance is now much larger do to the opening switch contacts. The voltage across the switch contacts will be whatever is necessary to maintain the current flow for the 5 time constants. After one time constant, the current will have dropped to 32% of the maximum current or in this case, 0.32 amps. If the resistance of the switch gap is 1 megohm, the the voltage will be 320,000 volts. More than enough to ionize the air and create a conductive path. If we assume an average resistance of 1 megohm, it will take 50 nS for the current to drop to 0. Of course during this time, the switch contact gets zapped. Placing a diode across the inductor such that the diode is reverse biased with the switch closed will give the current an alternate path as the polarity of the inductor reverses when the magnetic field collapses and the inductor becomes the source. This lowers the voltage from 1,000,000 volts to 0.7 volts. The downside is that the time it takes for the current decrease increases bo the ratio of 1,000,000/0.7. In a relay, this may cause the relay to "chatter" when opening. Adding a zener diode in series anode to anode with the spike suppressing diode will alleivate most chattering problems. A 34.3 volt zener will raise the voltage from 0,7v to 35v and shorten the time by a factor of 50 (35/.0.7).
The reactance of a capacitor is proportional to?
inverse of frequency
AnswerReactance is inversely-proportional to frequency of the supply, and the capacitance of the capacitor.
parallel
A device that gives power to a circuit?
A battery or eletrical generator would do that.
AnswerYour question should be rephrased. You do not 'give power' to a circuit. 'Power' is simply a rate -the rate of doing work.
What three conditions in a Barkhausen criterion must be met for oscillation to occur?
The Barkhausen stability criterion is just an obvious observation. It is a necessary but NOT sufficient criterion for oscillations.
The Barkhausen stability criterion states that an oscillator will oscillate when the total phase shift from input to output and back to input is an integral multiple of 360 degrees and the system gain is equal to 1.
The proper Barkhausen topology is defined as a loop of an amplitude determining inverting nonlinear amplifier (four terminal two-port ) and a linear passive frequency determining feed-back four terminal two-port circuit. It is obvious that the loop gain is 1 and the phase shift is a multiple of 360 degrees when the loop is closed. The Barkhausen criterion is necessary but not sufficient.
Question: Who was the first to open the loop and claim that the criterion is sufficient ?
Linear oscillators are mathematical fiction. Statements like "the non-linear characteristic will bring the poles to the imaginary axis" are of course nonsense. The bias-point of the amplifier will vary with time so the small-signal model of the circuit will vary with time i.e. the eigenvalues of the linearized Jacobian of the differential equations will move around with time in the complex frequency domain. The mechanism behind the steady state behavior is a kind of energy balance. Energy is received from the power source when the poles are in RHP. Energy is dissipated in the loss elements when the poles are in LHP. The frequency is a kind of time average of the imaginary part of the complex pole pair. The Barkhausen criteria is just the obvious observation that the gain around the closed loop of an amplifier and a feed-back circuit is 1 (one) and the phase-shift is 0 (zero or a multiple of 2pi). The Barkhausen criteria is NOT sufficient for start-up of oscillations. Phase-noise is an expression for the variation of the imaginary part of the complex pole-pair during the period of the oscillations.
What is amplifier and what is the general circuit of amplifier?
An amplifier amplifies voltage or current. The most basic amplifier consists of a transistor where a signal is fed into the base and is output to the emitter or collector.
For simple, low frequency applications (not RF), it may be simpler to use an operational amplifier (op amp) than designing your own amplifier. Also, the data sheets provide very helpful schematics for creating an amplifier. A very common one is the 741; these are also fairly cheap.
What is the angle between magnetic fields on a three phase motor?
You have to sort of visualize the composite EM Field from the 3 phases. The 3 phases are offset 120 degrees from each other. Imagine 3 electromagnets in a straight line. Each magnet is connected to one of the phases. If the first one to the left is at peak (max magnetic field is over it), the other 2 are at less than peak, but the current in the left magnet is falling while the current in the center and right are building. The right is farther behind===> Center reaches peak first (Now the peak magnetic field is over the center). But the center current is falling while the right continues to build to peak. Now the peak magnetic field is over the right and the left has been building again ===> The magnetic field moves over the left again and the cycle repeats.
Now bend those 3 magnets into a circle ===> rotating field.
What difference's between potential transformer and voltage transformer?
Both are same. This is an instrument transformer used for metering & protections.
Real time applications of induction motors?
Domestic fans, refrigerators, blowers, electric bikes, etc........
What is a line differential protection?
Differential protection for power transmission systems comes down to looking at power coming into a location and power leaving that location; if these are equal, then everything is OK. If these are not equal, meaning power is going in and not coming back out, this indicates a fault condition. An example of differential protection is for a substation bus. current transformers are connected to the bus differential from every power sourch into and out of the bus. The bus differential adds all the currents up, and the sum should be zero. If it is not, this means current is flowing into the bus but not leaving, meaning it is going to ground somewhere.
A line differential is the same concept as a bus differential. It's simply covering a line, which can be many miles long, so usually two relays are used, connected by a high speed communication path such as fiber optic cable. The current flowing in one side should be equal to the current flowing out the other.
Why three phase motors are self starting?
Because the three phases are 120 degrees apart which kind of gives a "rotational magnetic field" as apposed to a two phase motor (your common 220 volt motor) where the phases are 180 degrees apart and the magnetic field opposes itself until the motor is spinning.
What is the main disadvantage of series generator?
Speed regulation in the series motor is quite poor.
VFD is an adjustable speed drive that is used mostly in electro mechanical drive systems that control AC motor speed. VFD has come down on cost and the size which improved performance through advance in switching devices.
What are the three prts of Volt Ohm Milliammeter?
It depends upon whether it is analogue or digital, as they work in completely different ways, and each will have completely different components. As there are far more than three 'parts' to either type of instrument, you need to rephrase your question and be more specific about what you want to know.
