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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
What is the formula for power in watts?
Electrical power is measured in watts. The formulas for power dissipated by a resistor are:
* P = V × I * P = V² / R
* P = I² × R P is power, V is voltage, I is current, R is resistance.
What are possible topics for tybsc it project?
I would suggest you visit some sites on the web, and you can even ask your queries and they reply to your queries very quickly.
Scroll down to related links and look at "Bandwidth and geometric mean".
How can an electromagnetic pulse destroy electronic devices?
One word:induction. When an electromagnetic pulse (EMP) hits, a big magnetic field "sweeps" everything in its path. The moving magnetic field (because it travels out from where it was created) will induce electromotive force (EMF) or voltage, if you prefer, in all kinds of stuff. There are tiny traces on circuit boards, and there are component leads and all kinds of conductors that are acting like little antennas inside electronic equipment. And these little antennae will "receive" the magnetic "signal" from the pulse and convert some of its energy into voltage. Because the pulse is so large, the voltage will be high, and will be high enough to damage components and circuits in all kinds of equipment. This will knock electronic devices out of commission. Permanently. Shielding is possible, but we can only do a limited amount of that. It's a whole are of investigation, and a lot of it is "top hush" because the applications for the shielding are mostly military. Looked at another way, if an EMP hits because someone set off a nuclear weapon, I'd rather that military aircraft fly and my computer go down than the other way 'round. Certainly the military would, too, and their budget pays for the work.
What are the applications of rectifiers in use?
A bridge rectifier, is a group of rectifiers (4 in a single phase) wired so that each half of an AC current is passed to respective positive and negative lines of a DC output.
It provides full wave rectification of AC into DC.
In a PN junction diode, the reverse current is due to the diffusive flow of minority electrons from the p-side to the n-side and the minority holes from the n-side to the p-side. Hence IS, reverse saturation current depends on the diffusion coefficient of electrons and holes. The minority carriers are thermally generated so the reverse saturation current is almost unaffected by the reverse bias but is highly sensitive to temperature changes. so , as the temperature increases the density of minority charge carriers increases creating a slight increase in the amount of IC.
so, the inference is reverse current is directly proportional to temperature
In the reverse biased condition the PN diode is least dependent on voltage till certain limit called breakdown voltage, till that voltage the increase in V is not actually increasing the current it is just increasing the heat at the junction which in turn raises the temperature and so the minority charge carriers.
But if the voltage increases the breakdown voltage the pn junction is lost and all the holes and electrons will start acting like charge carriers , such avalanche of charge carriers increases the current sharply to several hundred times. This phenomena is called as zener or avalanche breakdown
so if applied voltage less than breakdown voltage
no significant change in reverse current(only due to minority charge carriers)
and if applied voltage greater than breakdown voltage
the pn junction break and current increases sharply (both due to minority and majority charge carriers)
What are the wavelengths of radiowaves?
Electromagnetic waves, such as radio waves and light waves, travel in a vacuum at 300,000,000 meters per second so the wavelength of a radio wave at any particular frequency can be calculated by using the formula:
[Wavelength in meters (m)] =
300,000,000 / [Radio frequency in cycles per second (Hz)]
AM (Medium and long wave) broadcasts:
Frequencies: 300 to 3,000 kilohertz (KHz)
Wavelengths in air: 1,000 meters to 100 meters
FM (UHF radio and television broadcasts):
Frequencies: 300 to 3,000 megahertz (MHz)
Wavelengths in air: 100 centimeters to 10 centimeters
How do you reduce 9V DC to 3V DC?
by using the step down transformer we can easily reduce the voltage.if we step down means the current(amps) icrease its vry useful for us
AnswerAs transformers are a.c. machines, you cannot use a transformer for this purpose. You will need to create a voltage dividercircuit -essentially a pair of resistors, of appropriate value, connected in series across the supply.
How do you stop FM radio frequency bleed?
We were tempted at first to recommend a tourniquet, but decided instead to ask for
clarification of what is meant by "bleed". That's a term with which our crack team of
telecom engineers is not familiar.
Why has an led light got a flat side?
The flat side marks the cathode, or negative wire coming out of the LED. Make sure that the wire on the flat side is connected to ground.
Transmitters before 1924 were long wave transmitters this is the lowest band in the RF spectrum 148.5 to 283.5 kHz. Propagation of shorter wavelengths was not understood until the shortwave experiments by amateur radio operators in 1923 and by Marconi in 1924. Spark-gap transmitters were used prior to World War I, until the development of powerful Radio alternators by General Electric just prior to the war. Vacuum tubes began to be used to generate radio frequencies in the mid-1920s.
After 1924, use of long wave radio for long distance communication began to decline, as much less expensive shortwave transmitters began to carry increasingly heavy volumes of long distance communication. A period of explosive growth of shortwave communications began in 1927, leading to rapid decline in long wave radio usage.
What is An example of a short circuit?
A short circuit is one that is characterized by extremely low resistance. This will result in the extremely dramatic increase of current. High current will flow until a safety device opens the circuit, or the weakest link in it burns out. And one of the two usually occurs in a moment or two.
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Short Circuit happens when the cables of the electrical appliances are worn out or it's not connected properly,a short circuit may occure.A short circuit has a very low resistance that almost all electric current flow through it.It'll affect the operation of the electrical appliances.Owing to the heating effect,the excess electric current would produce a large amount of heat,wihout a fuse or a circuit breaker,a fire may be occured when there's a short circuit.
What is the operating frequency of cellular communication?
There are two main types of Cellular phone com usage, that being CMDA and GSM.
GSM operates, typically in a range of 850mhz, 900mhz, 1800 and 1900mhz. In parts of Europe it also uses 2100mhz. Older GMS specs can go as low as 380mhz for uplink and downlink and the channel will vary.
CDMA operates at usually at 800mhz or 1900mhz. Some of the 4g WiMax signals can run as high as 2.7ghz. That however is used for data, not for voice mode.
Again, different variations of this will run at other speeds but those are the most common ones.
What is the working principle of the thermistor?
A thermistor changes it's resistance depending on temperature. Hence Thermal-Resistor. (Thermistor)
It is all to do with the crystal structure of the substance the thermistor is made of.
Some increase their resistance as temperature rises, called Positive Thermal coefficient, 'PTC'.
Others reduce their resistance with increasing temperature, called Negative Thermal Coefficient. 'NTC'.
They can be used in a feedback loop of a simple amplifier and switch circuits, to control temperature of a device.
They can be calibrated for use in a current loop, to directly measure temperature, like a thermometer.
They can be used to stop surges in start up circuits, initially giving a high resistance until things warm up. Or used to apply a large current and then reduce as things warm up. (Like in the old degaussing coils on a colour CRT).
When a 60 Hz voltage is applied to the input of half wave rectifier what is input freequency?
The relationship of the input frequency and output frequency in a half-wave rectifier is one-to-one.(For full-wave, its one-to-two.)
The shape won't be the same, as the rectifier will only pass alternate half-cycles, but the apparent frequency will be the same.
Reactive power is an odd topic in AC (Alternating Current) power systems, and it's usually explained with vector mathematics or phase-shift sinewave graphs. However, a non-math verbal explanation is possible.
Note that Reactive power only becomes important when an "electrical load" or a home appliance contains coils or capacitors. If the electrical load behaves purely as a resistor, (such as a heater or incandescent bulb for example,) then the device consumes "real power" only. Reactive power and "power factor" can be ignored, and it can be analysed using an AC version of Ohm's law.
Reactive power is simply this: when a coil or capacitor is connected to an AC power supply, the coil or capacitor stores electrical energy during one-fourth of an AC cycle. But then during the next quarter-cycle, the coil or capacitor dumps all the stored energy back into the distant AC power supply. Ideal coils and capacitors consume no electrical energy, yet they create a significant electric current. This is very different from a resistor which genuinely consumes electrical energy, and where the electrical energy flows continously in one direction; moving from source to load.
In other words, if your electrical appliance contains inductance or capacitance, then electrical energy will periodically return to the power plant, and it will flow back and forth across the power lines. This leads to an extra current in the power lines, a current which heats the power lines, but which isn't used to provide energy to the appliance. The coil or capacitor causes electrical energy to begin "sloshing" back and forth between the appliance and the distant AC generator. Electric companies must install heavier wires to tolerate the excess current, and they will charge extra for this "unused" energy.
This undesired "energy sloshing" effect can be eliminated. If an electrical load contains both a coil and capacitor, and if their resonant frequency is adjusted to exactly 60Hz, then the coil and capacitor like magic will begin to behave like a pure resistor. The "energy sloshing" still occurs, but now it's all happening between the coil and capacitor, and not in the AC power lines. So, if your appliance contains a large coil induction motor, you can make the motor behave as a pure resistor, and reduce the current in the power lines by connecting the right value of capacitance across the motor coil.
Why is reactive power so confusing? Well, the math is daunting if not entirely obscure. And the concept of "imaginary power" puts many people off. But this is not the only problem. Unfortunately most of us are taught in grade school that an electric current is a flow of energy, and that energy flows back and forth in AC power lines. This is completely wrong. In fact the energy flows constantly forward, going from source to load. It's only the charges of the metal wires which flow back and forth.
Imagine that we connect a battery to a light bulb. Electric charges already present inside the wires will begin to flow in the circle, and then electrical energy moves almost instantly to the light bulb. The charge flow is circular like a belt, but the energy flow is one-way. Now imagine that we suddenly reverse the connections to the battery. The voltage and current will reverse... but the energy still flows in the same direction as before. It still goes from battery to bulb. If we keep reversing the battery connections over and over, we'd have an AC system. So, in an AC system, only the voltage and current are "alternating," while the electrical energy flows one-way, going from source to load. Where AC resistive loads are concerned, electrical energy does not "alternate." To understand energy flow in AC systems, it's critically important that we understand the difference between charge flow (current, amperes) and energy flow (power, watts.)
What is imaginary power? Simple: it's the unused power which flows backwards and forwards in the power lines, going back and forth between the load's coil or capacitor and the distant AC generator. If your appliance was a pure capacitor or inductor, then it would consume no electrical energy at all, but instead all the flowing energy would take the form of "sloshing energy," and we'd call it "imaginary power." Of course it's not actually imaginary. Instead it's reflected by the load.
What is real power? Even more simple: it's the energy flow which goes continuously from the AC generator and into the appliance, without any of it returning back to the distant generator.
Finally, what is "apparent" power? It's just the combination of the above two ideas: it is the continous-forward-moving or "real" energy flow, combined with the sloshing or "imaginary" energy flow.
What is the period of a 250Hz sine wave?
The period is the reciprocal of the frequency, in this case, 1/250 second.
Difference between a diode and a transistor?
diode is a bipolar device and transister is a three terminal device
a diode will conduct any time there is a positive voltage from cathode[-] to anode[+] following an exponetial curve of the diode.
a transistor can control the same exponential curves by a voltage applied to the base.
Why tungsten filament does not obey ohm's law?
A tungsten filament does follow Ohm's Law at any instant of time. You may be confused in that the filament resistance changes from its "cold" state to its "hot" state. When cold the resistance is about 1/15 the resistance of what it is when the filament heats up, which happens very quickly. At any instant Ohm's Law holds. When the voltage is applied you have an initial current draw that exceeds the steady state current draw based on the change in resistance.
AnswerOhm's Law either applies, or it does not. It cannot apply 'at an instant of time' -a change in current is either proportional to a change in voltage, or it isn't!
A tungsten filament does not obey Ohm's Law, because the current flowing through the filament does not increase in proportion to the applied voltage. This is because the resistance changes due to the filament's increasing temperature as the applied voltage increases. This is why Ohm's Law specifies that current is proportional to voltage, provided the temperature remains constant.
Although tungsten doesn't obey Ohm's Law, the so-called Ohm's Law equation applies whether a circuit obeys Ohm's Law or not. This is because the formula is really derived from the definition of the ohm, and not from Ohm's Law itself, which makes absolutely NO reference to resistance!
How do you find the branch current in parallel circuit?
For each individual branch, you can use Ohm's Law - just divide the voltage by the resistance.
A current flowing towards the viewer in a cross section conductor is shown by?
Sketch the direction line of force around a conductor which is carrying current away from the viewer and also towards the viewer.
How is total capacitive reactance for parallel capacitors using their reactances is calculated?
Total capacitance for parallel capacitors is simply the sum of all capacitor's individual capacitances. This would apply within (reasonably) any frequency, ignoring non-ideal resistance and inductance, so the same can be said for capacitive reactance.
