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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
Resistance: Electrical resistance describes how an electrical conductor (a wire) opposes the flow of an electrical current (flow of electrons). To overcome this opposition a voltage (a energy) must dropped (used) across the conductor (wire). Resistance can be described by ohms law: Ohms Law: R = V / I (Resistance = Voltage / Current) (resistance measured in ohms) where: Voltage [V]= the energy lost across an component (voltage measured in volts). Current [I] = the charge (electrons) flowing through an component (current measured in Amps). Electrical resistance can be thought of as sticking your hand out a car window. The faster [current] you drive the harder the wind presses [resistance] against you hand and therefore it takes more energy [voltage] to hold your hand steady. When trying to overcome electrical resistance, the electrical energy lost is turned into heat. This is how the elements of a household stove, toaster, and fan heater work. Because of the vacuum in a light bulb, the electrical energy lost is instead turned into light. It can be seen the electrical resistance plays a large role in modern life. Resistor: The resistor is the most common electronic component and is used to limit and/or control the voltage and current in an electronic circuit. Resistors are carefully manufactured to provide a predetermined value of electrical resistance which may range from 0.1 ohms to 100,000,000 ohms, depending on the application. The physical size of a resistor also varies dependant on the amount of power passing through the resistor, given by: P = V x I (Power = Voltage x Current) (power measured in watts) There are also many types of resistors including: · Variable Resistor - changes resistance when its shaft is rotated (volume knob on a stereo). · Thermistor - changes resistance when the temperature changes (used in a thermostat). · Light Dependant Resistor (LDR) - changes resistance when the lighting changes (used in children's night-lights). Resistor Example: An LED is a small red light (such as the one on the front of most TVs) and requires 2.0 volts and 0.02 amps to operate correctly. If we connected that LED up directly to a 12 volt battery, the voltage would be too high, and too much current would flow… the LED would blow up. We need to use a resistor to limit the voltage and current. But which value of resistance should the have resistor? Uses ohms law: R = V / I = (12.0 - 2.0) / 0.02 = 500 ohms (Note: the voltage across the resistor is the battery voltage minus the voltage we want across the LED) But which value of power should the resistor be capable of handling? P = V x I = (12.0 - 2.0) / 0.02 = 0.2 Watts
Note: k = x1,000 M = x1,000,000 G = x1,000,000,000
So a 10k resistor = 10kohms = 10,000ohms
What happens in series resonance?
The properties of a series alternating-current L-R-C circuit at resonance are:
- the only opposition to current flow is resistance of the circuit
- the current flowing through the circuit is maximum
- the voltage across the resistive component of the circuit is equal to the supply voltage
- the individual voltages across the inductive and capacitive components of the circuit are equal, but act in the opposite sense to each other
- the voltage appearing across both the inductive and capacitive components of the circuit is zero
- if the resistance is low, then the individual voltages appearing across the inductive and capacitive components of the circuit may be significantly higher than the supply voltage
How does voltage drop effect the amps?
Yes. When the voltage drops and the power requirement (watts) stays the same, the amperage goes up.
Why are electric meters connected in series with the rest of the circuits in the house?
Electric meters are connected in series with the rest of the circuits in the house because, that way, the meter can measure the current used by all of the circuits in the house. The meter integrates and records the current as power in kilowatt-hours.
Another Answer
Actually, energy meters are not simply 'connected in series' with the rest of the circuits in a house.
In simple terms, an analogue energy meters contain twocoils: a current coil and a voltage coil. The current coil is, indeed, connected in series with the rest of the household circuits, but the voltage coil is connected in parallelbetween the line and neutral conductors. This means that the energy meter is monitoring the (in-phase) load current and the supply voltage, and the torque produced by the resulting magnetic fields is proportional to the power of the load.
Power is a measure of the rate of energy consumption and, so, to determine the energy consumed by the load, the meter's combined magnetic fields drive a disc which, as it rotates, drives dials that record the amount of energy consumed over a given period (between meter readings). Energy (notpower!) is expressed in kilowatt hours (kWh).
AND gates are used to combine multiple signals, if all the signals are TRUE then the output will also be TRUE. If any of the signals are FALSE, then the output will be false.
ANDs aren't used as much as NAND gates; NAND gates use less components and have the advantage that they be used as an inverter.
ANSWER: And is a logical function of two or more implication. To make a statement to be true all inputs must be true otherwise the output is false. While the applications are extensively used in computer. This function was used long before computer as a logic discussion or statement. JFK believe in equality the Russians also believe in equality does it make JFK a communist? by implication it does.
What is the maximum power using USB port?
That varies dramatically depending on the revision of the USB used on the port.
5 ohms...
What happens to the current when you unscrew the bulb in a circuit?
If the wiring is in series, the entire circuit is cut and the current is zero. If the wiring is in parallel, the current decreases. I'm too occupied to write out formulas and examples on hypothetical scenerios, but the current decreases with lessened loads. C'mon! You didn't know that??...
A transistor have 3 legs. B, C and E.
You can measure the resistance between the legs with a multimeter in order to get a good indication of its condition.
If the resistance between any of the 3 legs are close to 0 Ohm (often 0.1 to 6 Ohm) then the transistor is most likely burned and no good any more.
If the resistance is above 200 Ohm, then the transistor is most likely burned as well.
Note:
A good transistor will measure different values depending on where you put probes. If the probes indicate an awful lot of resistance then try to switch the probes and measure again. If resistance is the same, then it is burned. If not, then it is likely OK.
It is often difficult to tell if your transistor is actually a Fet or a Darlington.
try to search internet for proper data on your 'transistor'.
Small signal transistors are often burned open between legs (very large resistance) where as large transistors often shortcut between legs (Very low resistance between legs).
I find the C and E leg to be easiest to diagnose a transistor on.
If the resistance both ways are the same, then it is no good.
Note:
In order to 100% determine a transistors condition, then you often would need to desolder it first. All the other components on a printboard will make it harder to diagnose (unless it has shortcut).
ANSWER: pay attention to the probes polarity and whether is an PNP or NPN . For an NPN The positive lead goes to the base and either other lead will show resistance reverse the leads and repeat now both reading should be hi resistance. For the PNP SAME PROCEDURE EXCEPT THE POLARITY OF THE LEADS ARE REVERSED
Current Amplification Factor or Current Gain is basically the ratio of the ratio of the output current to the input current when its passing through an electrical device. So, it gives us the amount of current gained as it flows through.
output current/input current
For example:for CE Transistor ,beta=ic/ib
How do you make power supply variable?
A variable power supply is one whose output voltage (or current) can be adjusted and therefore set to a desired figure. They are used in development and design odf circuits, eliminating the need for possibly many power supplies of different output voltages.
Once a circuit is connected to it, the output would not normally be changed.
When there is a difference in voltage the flow of charge is called?
flow of charge is called current.
but the direction of flow of current is always taken oppsite to the flow of charge.
What is the definition of a steel wired armoured cable in electrical engineering?
Underground cables are 'armoured' in order to protect them against mechanical damage. This armour takes either of two forms: (1) steel tape, or (2) wire. Wire armour tends to be used on cables with a larger diameter, as it makes them more flexible compared to cables with tape armour.
In both cases, the armour is spiral-wound towards the outer part of the cable along its length and is, itself, protected with a hessian or plastic outer layer.
What is the use of buffer circuit?
One prominent application is this:
Some circuits have an output impedance very high. If these circuits are coupled with another circuit of low input impedance, the desired functionality of the latter circuit will be drastically affected. Because the first circuit tries to deliver large voltage to the second and the second invariably requires small input voltage.
To avoid the circuit disfunctionality, a buffer circuit (a circuit with high i/p impedance and a low o/p impedance) is used.
Another application is in the delay matching. This is an advanced topic though. The technology is still new.
In delay matching, the latter circuit requires a delay of say "n" seconds after the first circuit's output. A buffer circuit is used in such cases also. The circuit design is totally different than the impedance matching case.
· A latch remembers the last state it was told to with another latching signal
· A buffer merely strengthens a signal so that it can be fanned out with integrity or drive a heftier device. Any amplifier is a buffer. It outputs a state only as long as the state persists on its input(s).
Why does voltage remain constant in the reverse breakdown region in a zener diode?
This space is for answering "http://wiki.answers.com/Q/Why_does_voltage_remain_constant_in_the_reverse_breakdown_region_in_a_zener_diode" Why does voltage remain constant in the reverse breakdown region in a zener diode?
What is semi controlled rectifier?
such a control rectifier that control or rectifier single phase. for that purpose we used SCR that is called single phase controlled rectifier.
Name two electromagnetic wave use to carry through an optical fiber?
We usually use some form of coherent light wave in fiber optic conduits to move data. That means a laser and the emission of light somewhere at or about optical wavelengths.
Is it possible to use class c amplifier in FM transmitter?
Technically possible, but not something you want to do. Once the carrier has been AM modulated, you need to handle it tenderly after that. Specifically, distortion has to be prevented, because distortion means new frequencies are introduced into the package, which makes the AM signal wider in occupied bandwidth ANDmakes AM sound terrible. Preventing distortion means the package can only be handled with 'linear' stages, and a Class-C stage is possibly the most non-linear kind of amplifier there is, since it's completely cut off for part of each RF cycle. By the way, this is the reason that AM is normally modulated in the RF power amplifier ... the last stage before the antenna. It would be a lot cheaper and easier to modulate at low level ... where much less audio power would be required ... and then RF-amplify the package for transmission, as is done in FM. But AM is so sensitive to distortion that it takes too much TLC to power-amplify it once it's been modulated. So amplifying (or frequency converting) are generally avoided after AM has been modulated.
Advantages of programmable logic array-PLA?
used as mux and demux , used for implement haff adder $ full adder, by program it
Why cmos is used more than other transistor?
Lower power dissipation (except at very very high switching rates, as almost all the power dissipated by CMOS is during switching).
What gate the output will be low for any case when one or more input are zero?
An inverter has a high output when the input is low, and a low output when the input is high.
