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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 won't a capacitor conduct DC?
capacitor blocks DC, after it finishes charging.
Actually, it resists any CHANGE to DC (ie ac), after it has finished charging. IRT the actual question, current will always flow, as long as there is a closed circuit.
What is the use of starter in tube light?
Tube light requires two things to function . Very high starting voltage , and high voltage to continue the operation . The starter is a circuit which breaks at regular intervals . When you break a circuit and start again , high voltage spark takes place . This voltage is further amplified through the choke which is a transformer . Thus at the beginning the starter gives high voltage sparks . Due to this the current begins to flow through the tube and the tube begins to glow. Once the tube starts , the required voltage to sustain is quite low , which is provided by the choke .
If the starter is bad the tube does not start . If the choke is bad or if the gas is low , the tube does not sustain its light .
Fluorescent starters are used in several types of fluorescent lights. The starter is there to help the lamp light. When voltage is applied to the fluorescent lamp, here's what happens:
- The starter (which is simply a timed switch) allows current to flow through the filaments at the ends of the tube.
- The current causes the starter's contacts to heat up and open, thus interrupting the flow of current. The tube lights.
- Since the lighted fluorescent tube has a low resistance, the ballast now serves as a current limiter.
Without the starter, a steady stream of electrons is never created between the two filaments, and the lamp flickers. Without the ballast, the arc is a short circuit between the filaments, and this short circuit contains a lot of current. The current either vaporizes the filaments or causes the bulb to explode.
The average 2 mw wind turbine produces a sound eqaul to 45 decibels
Was electricity used to supply light and power to US factories?
After about 1890, yes. The use of electricity for lights was far safer than the previous alternative of gas lamps.
Why must do the insulation testing in circuit?
Insulation resistance testing involves applying a voltage across a dielectric, and measuring the resulting current and resistance. However, in order to get a proper reading, any electrical charge still within the system needs to be taken out, so as not to mess with the readings.
How do you tell the difference between AC and DC 3 phase generators and alternators?
The very first thing to do is look at the nameplate. There it will tell you what the voltage is. On a three phase generator there is usually no places to plug any equipment into. Three phase generators usually have the coil ends brought to terminal points in the generators junction box. From a second set of terminals the feeder wires go to the top end of the generators main disconnect breaker. Different voltages can be obtained by positioning jumpers between different terminals within the junction box.
What is difference between amplitude and peak value?
It is the highest value of the amplitude, called the peak value. Scroll down to related links and look at "RMS voltage, peak voltage and peak-to-peak voltage". Look at the figure in the middle below the headline "RMS voltage, peak voltage and peak-to-peak voltage".
What is the Relationship beteen Capacitance and frequency?
The short answer to the question is the capacitive reactance of a capacitor in a DC circuit is infinite.
In a DC circuit, disregarding transient behavior and any leakage effects, a capacitor is effectively an open circuit, and so its reactance is essentially infinite.
Capacitive reactance is calculated as Xc =1/(jwC) where w is the angular frequency in radians per second, w = 2*pi*f, C is in Farads, and f is in Hertz.
With DC, both f and w are zero, and, theoretically, the formula,
Xc =1/(jwC) = limw-->0 [1/(jwC)] becomes infinitely large. In any practical circuit, however, there is always some leakage, so the impedance of the a capacitor will be quite large, on the order of megohms, but still finite.
What is the full form of IGBT?
The full form of igbt is insulated gate bipolar transistor.
it is constructed from the combining of both BJT and PMOSFET.
it has high input impedance and low on - state power loss .
it is free from second break down problem present in bjt...
it is also known as (MOSIGT), (COMFET)...
it is constructed virtualy in the same manner as a power
MOSFET.an IGBT has also thousand of basic structure cells
connected appropritely on a single chip of silicon.
it has a four substrate p,p+,n+,n-. respectively...
p+ substrate is called injection layer because it injects
holes into n- layer .n- layer is called drift region .
thickness of the n- layer determines the voltage blocking
capability of IGBT.
the p layer is called body of the IGBT.
WHERE IT IS USED : it is widely used in medium power
application such as DC and AC motors drives.
UPS SYSTEMS , RELAYS AND CONTACTORS.
In thyristor the gate is triggered the gate is losses its
control. ie if we remove the gate pulse after the thyristor
starts conducting it will not stop.
but in IGBT we can control the Gate. by applying reverse
voltage applied across it .
The Thyristors can not be switched beyond 1kHz where as
IGBTs can be switched upto 25kHz and even to 100KHz with
few soft switching techniques.
The thyristor can carry very high currents order of 3000A
but IGBT carries less current max of 1000A.
Thyristor commutation ,that is switching off is very
difficult. But there are applications of Thyristor with
natural commutation.
The IGBT can be switched on and off like a MOSFET. ie it is
voltage controlled device.
How would you measure a relays contacts resistance?
The voltage drop across a relay coil will be the same as the coil supply voltage. If you are trying to see if the coil is good or not, remove one of the voltage supply leads and check for continuity by using an ohm meter across the coil leads. A reading will tell you that the coil is intact and not open.
If the resistance of the wire is 20 ohms and the voltage between the two ends of the wire is 20 volts,
then the current through the wire is
I = E/R = (40/20) = 2 amperes.
Voltage frequency inverter dc or ac output?
An inverter changes a d.c. input to an a.c. output.
Inverter is a device to change low
volt DC to high volt AC
12 Dc to 220 Ac volt
So many type of inverter of watts
500 watt 1000 watt 5000 watt
Current, by Ohm's Law, is voltage divided by resistance, so, 18 volts divided by 2 ohms is 9 amperes.
Where is microwave communication used?
They were first used to communicate. A worker on an active antennae noticed that while it was sending microwaves out, a candy bar melted in his shirt pocket. He then designed a box that would capture and reflect these microwaves to heat up food and liquids. We call it the microwave oven.
What is the voltage drop through a resistor of 6 ohms(2amps)?
Assuming the these resistors are connected in series, the voltage drop across each resists can be calculated simply using V = IR. In a series circuit, the same current must flow through each resistor. So, 2*i + 2*i + 2*i = 6 volts. or i * 6 = 6, or i = 1. So, the voltage drop across all resistors i*r is 2 volts.
The output voltage from a PC power supply are?
Generally, there will be a 12+ volt rail, a 5+ volt rail and often a 3+ volt rail.
Why should an ohmmeter never be used on an energized circuit?
Because an ohmmeter works by putting a potential difference (voltage) across a load and measuring the resulting current (the current will be inversely proportionate to the resistance). In a live circuit there is already current flowing through the load so (at best) the reading will be inaccurate, at worst the meter will be damaged.
What is status of a circuit that is complete and unbroken with flowing electric current?
A circuit that is complete and unbroken with flowing electric current normally has steady supply of voltage with no broken links. Electrical energy flows to light up a bulb or do similar work. Its status is complete, nothing else is needed.
Are microwaves dangerous to humans?
As long as it hasn't been damaged in any way and is taken care of, a microwave can be used for many years - my own parents are using both a standard microwave and a combination microwave/conventional oven that they've owned since 1982.
The main health hazards with microwaves are to people with pacemakers and similar type medical implants - not all microwaves are taken care of the same.
AV stands for Audio Visual, i.e. engineering systems in sound or video production, encompassing TVs, monitors, receivers, amplifiers, soundbars and so on. All of those components requires electronic design to create in the first place, and also to some extent some knowledge of electronics can be a help in building AV systems that are constructed from many discrete components.
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
Why consider only 3dB for bandwidth calculation?
3dB of gain rolloff is a linear reduction of gain by a factor of 2. That makes it a good reference point.
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
