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Electronics Engineering
Electronics Engineering is a branch of engineering that deals with practical applications of electronic components, devices, systems, or equipment. Electronics are devices that operate on low voltage sources, as in electron tubes, transistors, integrated circuits, and printed circuit boards and use electricity as part of its driving force.
24,372 Questions
Why current lead voltage in coil?
because a coil is an inductor,for current leads voltage in an inductor
AnswerIt doesn't! Current lags voltage in a coil. In a purely-inductive circuit, the current lags the supply voltage by 90 degrees. The reason for this is 'self inductance'. Whenever a current changes, a voltage is induced into the coil which opposes that change in current. The maximum self-induced voltage occurs when the rate of change in current is greatest. The greatest positive rate of change of a.c. current occurs when that current is passing through the zero axis of its waveform, so the greatest (negative) induced voltage occurs at thatsame point, which is one-quarter of the wavelength, or 90 degrees. In accordance with Kirchhoff's Voltage Law, the supply voltage must be in antiphase with the induced voltage. So when the peak induced voltage is negative, the peak applied voltage must be positive. Or, to put it another way, the peak value of the applied voltage must occur 90 degrees before the peak value of the current -so the current lags the applied voltage by 90 degrees.
Does voltage regulator increase or decrease the current input?
A DC voltage regulator gives a constant output voltage provided the input voltage is at least 1.5 v higher, up to a given limit. The input current is slightly more than the load current, because a small amoutn of current is needed for the voltage regulator circuit. Check the datasheet of the component which you are using to find the limits. 7805 IC can give upto 1A of current if there is adequete heatsinking.
Why were researchers looking for a replacement for vacuum tubes?
Bell Labs researchers were unsatisfied with the low reliably, high power usage, and large size of the vacuum tubes that needed to be used in the telephone switching and long distance trunk systems of the 1940s.
A semiconductor laser is a type of laser which utilizes a semiconductor as its Photon source, rather than a gas (Argon, CO2, Etc...) laser which uses inert gas as an active medium.
Many physicists and engineers consider a semiconductor laser a type of "Solid-State" or "Two-State" LASER.
The resistance of a liquid to flowing is what?
The resistance of a liquid to flowing is its viscosity.
Viscosity is a property arising from friction between neighboring particles in a fluid that are moving at different velocities. In liquids, it could be considered the "thickness". For example, maple syrup has a higher viscosity than water.
This answer simplifies for the purpose of answering the question asked.
A ULN2803 is an Integrated Circuit (IC) chip with a High Voltage/High Current Darlington Transistor Array. It allows you to interface TTL signals with higher voltage/current loads. In English, the chip takes low level signals (TLL, CMOS, PMOS, NMOS - which operate at low voltages and low currents) and acts as a relay of sorts itself, switching on or off a higher level signal on the opposite side.
A TTL signal operates from 0-5V, with everything between 0.0 and 0.8V considered "low" or off, and 2.2 to 5.0V being considered "high" or on. The maximum power available on a TTL signal depends on the type, but generally does not exceed 25mW (~5mA @ 5V), so it is not useful for providing power to something like a relay coil. Computers and other electronic devices frequently generate TTL signals. On the output side the ULN2803 is generally rated at 50V/500mA, so it can operate small loads directly. Alternatively, it is frequently used to power the coil of one or more relays, which in turn allow even higher voltages/currents to be controlled by the low level signal. In electrical terms, the ULN2803 uses the low level (TTL) signal to switch on/turn off the higher voltage/current signal on the output side.
The ULN2803 comes in an 18-pin IC configuration and includes eight (8) transistors. Pins 1-8 receive the low level signals, pin 9 is grounded (for the low level signal reference). Pin 10 is the common on the high side and would generally be connected to the positive of the voltage you are applying to the relay coil. Pins 11-18 are the outputs (Pin 1 drives Pin 18, Pin 2 drives 17, etc.).
The ULN2803 package is available from many manufacturers, you can download a datasheet at the link below.
A metal film capacitor is an electrical part that holds energy electrostatically inside of an electric field. The capacitor has a dielectric which separates two electrical parts which are made out of thin film.
How do electronic video projectors project black?
Black is considered as the `absence of light', or the complete absorption of the visible spectrum, from which no light reflects.
In video projectors, the light is completely blocked from reaching the screen, creating the same effect. It appears to be black because you're usually watching it in a darkened room and in relation to the brighter areas on the screen, your mind perceives it as being black. In reality, if you were to look at the screen, you'd still see that there's no light hitting it to reflect back to your ryrs from the screen.
What are the advantages of clap oscillator?
clapp oscillator have frequency more stable and accurate than colpitts oscillator.
What is the working principle of semiconductor laser?
The principle of semiconductor laser is very different from CO2 and Nd:YAG lasers. It is based on "Recombination Radiation"
The semiconductor materials have valence band V and conduction band C, the energy level of conduction band is Eg (Eg>0) higher than that of valence band. To make things simple, we start our analysis supposing the temperature to be 0 K. It can be proved that the conclusions we draw under 0 K applies to normal temperatures.
Under this assumption for nondegenerate semiconductor, initially the conduction band is completely empty and the valence band is completely filled. Now we excite some electrons from valence band to conduction band, after about 1 ps, electrons in the conduction band drop to the lowest unoccupied levels of this band, we name the upper boundary of the electron energy levels in the conduction band the quasi-Fermi level Efc. Meanwhile holes appear in the valence band and electrons near the top of the valence band drop to the lowest energy levels of the unoccupied valence energy levels, leave on the top of the valence band an empty part. We call the new upper boundary energy level of the valence band quasi-Fermi level Efv. When electrons in the conduction band run into the valence band, they will combine with the holes, in the same time they emit photons. This is the recombination radiation. Our task is to make this recombination radiation to lase
What is the current value of a 1993 Chevy Suburban?
"http://wiki.answers.com/Q/What_is_the_current_value_of_a_1993_chevy_suburban"
Will an ac unit run on modified sine wave?
The unit should run OK on a modified sine wave since motors are not that sensitive to the waveform. Efficiency might be slightly reduced.
The real problem may be in starting the unit. If the input does not have enough power to allow the compressor to start properly and it stays running on the start winding, it could burn up the start winding. Checking the current input with a clamp-on style amp-meter should show if it is drawing excess current by running on the start winding.
How capacitor cancels inductive effect?
A capacitor try to leads the current while a inductor tries to legs the current so they cancels each other's effect ....
Radio Shacks 25 ohm rheostat works very well to the point where on the slow end, you have to give it a kick start if you turn on the power when it is on that side. If it is already running, it will continue to run (no load) at the low end.
What is the circuit diagram of current series with closed loop gain?
- Your mom's awesome!! HAAHAHAHAH I m just kidding BRO ....
Are electric heaters connected in series or parallel?
Some are series, some parallel, some both. Depends on the design. Series heaters will have all the heaters fail or shut off should one burn out or open circuit. Should a series heater short out the other heaters will see increased voltage so must be able to handle full voltage or they will overheat and fail.
Parallel heaters will not notice if one of the others open circuit. If protection devices, such as fuses or overloads or overtemp, are installed for each heater all others will continue to operate if one shorts out or fails.
Parallel heater designs are more common.
Does the size of a capacitor matter?
Yes, the size of a capacitor "matters" just as much as the size of a resistor "matters". In both a capacitor and a resistor "size" refers not only to the electrical value of the item but to its current-carrying capacity: a small resistor will burn up if you try to push too much current through it. A big resistor will be able to carry a much higher current than a small one having the same resistance value.
Similarly, a small capacitor will be destroyed if you try to push too much current through it and a big capacitor will be able to carry a much higher current than a small one, even if both have exactly the same capacitance value. Capacitance values are measured in Farads (F), microFarads (uF) and picoFarads (pF). Just as a resistor has "Resistance " measured in Ohms, a capacitor has "Capacitive Reactance" or "Impedance", measured in Ohms.
The Impedance of a capacitor varies with the frequency of the alternating current passing through it. (This is quite different behavior to a resistor: the Resistance of a resistor does not change with the frequency.) If you look in a book about electrical engineering components you will be able to learn how the Capacitive Impedance is calculated according to the frequency. "The impedance of a capacitor is inversely proportional to the frequency - that is, for very high-frequency alternating currents the reactance approaches zero - so that a capacitor is nearly a short circuit to a very high frequency AC source. Conversely, for very low frequency alternating currents, the reactance increases without bound so that a capacitor is nearly an open circuit to a very low frequency AC source. This frequency-dependent behaviour accounts for most uses of the capacitor." [From Answers.com]
What is the difference between flip flops and sandals?
Flip flops, fashioned after Japanese footwear called "zoris", are held onto the foot by two thongs that rise from the side of the sole and meet and attach to the sole between the first and second toe of the wearer. Sandals are footwear of the type worn in the Roman Empire. They are usually manufactured of leather, and are held onto the foot by several thongs across the instep, and a strap behind and above the heel of the wearer.
What is the difference with a linear and nonlinear scale?
The differences between the these two is that linear scale shows the relation between the map distance and the ground distance. The nonlinear scale do not show the relation between the map distance and the ground distance.
Why embedded Systems demand have increased Today?
Why embedded Systems demand have increased Today ?
http://corvalent.com/02c_embedded_system...
What happens to electricity not used from a generator?
As far as I know, all generators produce a voltage. If there is nothing connected across it, then no energy is produced.
If there is some kind of load connected to it, then electrical energy flows into the load. Any energy that is wasted by the generator itself, the transmission lines, or the load itself changes into heat energy.
It might depend on the generator, though. I guess some might need to be "on" at all times to run properly. Although the turbines don't need to put out energy all the time, a nuclear power plant does produce thermal energy at all times that it is on. In that case, they'd have a big load nearby to use the otherwise wasted energy in. The best case would be to put that waste energy to use, in a nearby desalination plant or refinery, for instance.
In March 1983 US President Ronald Reagan put forward his Strategic
Defense Initiative, more popularly known as Star Wars which was to act
as an antimissle defense shield.
