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Circuits
Overachieving and under-appreciated, circuits are the foundation that our technological society is built on. Now's your chance to find out not only how they work, but why. Questions regarding the physics behind voltage, resistance, capacitance, inductance, transistors, LEDs, switches, and power supplies; and how they're used to create analog and digital circuits, should be directed here.
1,646 Questions
What are all of the different electrical voltages in the US?
This is your lucky day. The standard mains supply
everywhere in the US is 120 V AC 60 Hz.
What does one-quarter W mean for a rated resistor?
It means that the resistor will safely dissipate the heat involved in transporting that much power through, without burning up/out. If you exceed that rating, the resistor will become too hot for its own good.
Power is always linked with Voltage and Current, and Current is linked with Voltage and Resistance of the resistor. You will do well to remember the tandem of laws:
Power [Watts] = Potential [Volts] * Current [Amperes]
and
Current [Amperes] = Potential [Volts] / Resistance [Ohms]
For example, if you have a 100ohm resistor rated at 0.25W, then to satisfy that requirement, a voltage of no more than 5V can be applied to it, because 5V / 100ohm = 0.05A, and 0.05A * 5V = 0.25W.
What should be done with unused TTL output?
Unused TTL inputs should never be left open. Depending on how their logic levels
will affect the operation you want from the device, unused inputs should always
be tied to either the +5v supply (logic 1) or to the circuit ground (logic 0). If an
input is left open ("floating"), then it can assume either logic level, and you literally
never know which state it's in.
Why CE configuration of BJT transistor gives 180 phase shift?
when the switch the emitter-base junection is an opnd circut and heance the value of input or base curent is zero.
Why diode rectifier need transformer?
A diode rectifier is a device (or four discrete devices- namely diodes), which converts alternating current (AC) into direct current (DC). It doesn't need a transformer as such. The transformer is there to convert the high voltage 'low energy' AC (like mains power) into low voltage 'high energy' AC (like 12V or 16V), which is then converted using the rectifier bridge into DC.
These are two separate devices, which nonetheless frequently appear together. This is because it is the easiest to transport power over large distances (say, from power plant to your house) using high voltage AC, so that a lot less energy is lost due to heat or weather along the way, but high voltage AC isn't the most useful form of energy for electronic devices. Electronic devices "like" the low-voltage (but 'high energy') DC, so the transformer first "steps the voltage down" (and "converts" the "volts" into usable "amperes"), and then rectifies it into DC, which is what many transistors (of which most electronics are made of) use to do some work for us (like playing a radio station).
So, the rectifier bridge doesn't need a transformer, but it is useful for many applications to have it.
Consider, on the other hand, your picture tube TV (the CRT ones, with the big, bulky rear ends?) - these picture tubes required high voltages, and so the line voltage wasn't stepped down using a transformer at all! In fact, it was actually stepped UP to the levels of several kilovolts needed to emit electrons which draw nice pictures on the front of the picture tube.
A Field Effect Transistor is a device with a single channel (conductor between two of the terminals). This channel is turned on an off by a voltage applied to the third terminal which is connected to the conducting channel in a J fet (junction Fet) or isolated from the channel in a Metal Oxide Semiconductor (MOS) fet. To keep the explanation simple, an enhacement mode MOS FET pulls charge carriers (electrons for N channel and holes for P channel) into the channel so its resistance decreases. This turns it on. By removing this voltage, charge carries move out of the channel and the FET turns off. It can be turned on partially by putting a small voltage on the control terminal called the GATE. In an N channel FET, the charge carriers (electrons) move from the SOURCE terminal (-ve) to the DRAIN terminal (+ve) when the FET is on. The voltage on the GATE is applied with respect to the SOURCE. In a P channel enhancement mode FET, charge carriers (holes) are also pulled into the channel in the same way but because the charge carriers are holes, the SOURCE is the +ve terminal and the DRAIN is the negative. The holes referred to are gaps in the crystal lattice of a substance like silicon which is doped (impurities added) with aluminum which has only 3 electrons in the outer shell instead of 4 like silicon. In a depletion mode FET, everything is the same except in reverse. Charge carriers are pushed OUT of the conducting channel.
How can millions transistors be in a single processor?
Thanks to the wonderful technology we now posess, a single transistor can be constructed out of two thin layers of material (P-doped and N-doped), and can be very, very small - as small as a few atoms, as some researchers have proved not too long ago! Therefore it is easy to put many such small transistors - in layers - on a small chip - the processor. Many of these, in mass production, have these transistors constructed on the micron scale (typically around 15 microns). If a transistor is 15 microns wide, you can put 66 of them in a milimeter, on just one layer, many of which construct a single processor die. It is now typical to have not millions, but billions of transistors on a single CPU!
Think about it: if you can put 66 transistors in a 15x15 micron area, you can fit about 11 108 889 (11 million) of them in a 5x5cm chip - and that's just one layer about a micron thick? Assuming the die itself is 4x4cm and is 3mm thick, each layer is 2 microns thick, and each transistor takes a 21x21 microns of space on a layer --- on such a processor die you would fit 5 442 175 500 - 5 and a half billion transistors.
Of course, these transistors switch very small currents - very small indeed! Your typical, run-of-the-mill discrete transistor can handle much larger currents, and its bulky body is designed to dissipate the heat generated in the process, as nothing else will cool it down. Processors usually have designated cooling methods (like radiators and fans) - without one, the temperature within one rises to "boiling" within seconds.
A failed diode electrically resembles a switch. Whether it resembles an
open switch or a closed one depends on the specific mode in which it
failed. But a bad diode won't behave like a diode any more.
Hertz Hurts
Can a resistor be installed backwards?
Resistors can be installed in any direction in a circuit. It doesn't matter in which direction you are installing a resistor. Resistor will resist the current in both sides of the connection. You can also apply capacitor in any direction for alternating current. Where as if you are concerned with direct current, a direction is needed to apply the connection
List 5 parts that all circuits have?
There are only three parts that ALL circuits have:
-- a source of electrical energy
-- components that dissipate electrical energy
-- good conductors to connect them together
Is Circuit switching is a method used to send data over the Internet?
yes it is
================
Answer #2:
No, it isn't. It's a great way to operate the modern telephone network of 1970,
but use it to send data over the Internet if you want to see the Internet instantly
go belly-up and sink beneath the waves of the foaming brine.
What is the resistance of the 12 volt circuit and has a measured current 0.25 A?
R = E/I = 12/0.25 = 48 Ω
If voltage regulator is bad what will it do to your vehicle?
It will either undercharge or overcharge the battery.
If the battery is subjected to overcharge for some period of time, it boils dry
and is destroyed. If it's undercharged, then you may not have the cranking
power that you need for starting..
If the voltage regulator is so bad that there's no output from it at all, then you
drive along normally for some distance, unaware that you're driving on only
battery, and then at some point you reach the end of the battery, suddenly
have no ignition, and putter to a stop. In this case also, the battery is probably
destroyed. And they ain't cheap any more. Better to check the regulator, and
install a new one if needed.
What is the voltage drop across a 12 ohm resistor with a source of 24 volts?
If there's nothing else between the ends of the resistor and the power supply, then
the voltage across the resistor is 24 volts, and the current through it is 2 amperes.
What is a doorknob capacitor used for?
Doorknob capacitor 's Application:
Marx Generator, MRI(Magnetic Resonance Imaging), Negative Ion Generator, Negative Air Ionizer, Negative Ionizers, Ozone generator, Ozone Machines, Polymer Housed Arrester, Polymer-housed Surge Arresters, Surge Arrester, Lightning Arrester, Surge Protection, Arrester, Lightning Current Arresters, Smart Grid,
You can check this Chinese doorknob capacitor manufacturer(www.hv-caps.com ),their engineer will reply your technical question and show you tech support, I have try it ,great and professional service.
What are the roles of a diode and a capacitor in an AC-DC converter?
An AC-DC converter you can operate a device on AC instead of batteries.
~bobbyjack~ : D
