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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
Difine the formation of p and n type semiconductors?
When a small amount of pentavalent impurity is added to a pure semiconductor , it is called n-type semiconductor , and , when a small amount of trivalent impurity is added to a pure semiconductor, it is called p-type semiconductor.
Which is faster latches or flipflops?
A D latch is level triggered. It will follow the input as long as the gate is true. Once the gate goes false, the output will stay at the last known value. A D flip flop is edge triggered. The output will not change until the edge of the gate. At that point, the output will go to the state of input, and then it will stay at that value.
Why you take 2Vm peak inverse voltage for full wave rectifier?
When the AC waveform goes to one peak, the capacitor that follows the diode is charged to that peak value. When the AC waveform goes to the other peak, the same diode is reverse biased between the alternate peak value and the charged value of the capacitor. This differential voltage is two times peak voltage.
What happens to electric current as voltage gets large?
If the resistance of the load is kept more-or-less constant, then the current also becomes larger. On the other hand, if the power of the load is kept more-or-less constant, then the current becomes smaller.
Since this is in the electronics section, I'll assume you mean a PNP transistor. PNP refers to the semiconductor layers used to make up the transistor. The P and N letters refer to positive and negative doping in the semiconductors, which changes the way electrons flow through the layers. This is a bipolar junction transistor (BJT), which can be thought of as a current amplifier. One P layer is called the emitter and the other is called the collector. The N layer is called the base. The emitter and collector are not usually interchangeable because they are made differently. When the voltage on the base is below the voltage on the emitter, usually by about 0.7 Volts, current flows from emitter to base. This allows a much larger current to flow from emitter to collector. This assumes the collector is at a lower voltage than the base, and is the usual connection. Similarly, there are NPN transistors.
How do you convert sound signals to binary?
By using an analog to digital conversion. To achieve this, samples of the waveform are taken at regular intervals. The human ear is capable of hearing audio frequencies up to 20 KHz, thus the sampling frequency needs to be at least twice as high in order to reproduce the highest frequencies without introducing too much distortion. Typically, samples are taken at a rate of at least 44,100 samples per second per channel for CD quality audio.
The amplitude of each sample is then scaled and converted to a signed integer. CD quality audio uses 16 bits per channel thus the waveform amplitudes are scaled to integers in the range -32,767 to +32,767. Thus CD quality stereo audio consumes 2 * 44,100 * 16 bits every second, which is 176,400 bytes per second. Thus 60 minutes of audio consumes approx. 605 MB.
How many 75K resistors must be put in parallel to provide a total resistance of 15K?
5000
For Parallel resistors:
Rtotal = R / N
Rtotal is total resistance
R = Value of resistors
N = number of resistors
15 = 75000 / N
N = 5000
Watts is the product of amps and volts. It's amps times volts. The watt (W) is a measure of power (P). It's the SI unit of power, actually, and it's a joule per second. The volt is a measure of electrical potential difference, and is the SI (derived) unit of electromotive force, or EMF (E). Voltage, which is measured in volts (V), is the force that drives electron current flow (I), which is measured in amps (A). In relationship to the volt, the watt is current flow times voltage, or, said another way, a watt is amps times volts. As regards watts and volts, they are "linked" by current. Let's look at the expressions: Power = Current x Electromotive force => P = I x E Power (in watts) = Current (in amps) x Electromotive force (in volts)
Voltage is a measure of electric potential, in joules per coulomb. Watts is a measure of energy transfer rate, in joules per second.
To complete the answer, amperes is a measure of charge transfer rate, in coulombs per second, which is why voltage (joules per coulomb) time amperes (coulombs per second) is watts (joules per second).
Classification of Continuous Time signals and Discrete time signals?
we often confuse our-self with continuous time and analog signals.
An analog signal is a signal which can take any amplitude in continuous
range that is signal amplitude can take infinite values on the other hand
a digital signal is one whose amplitude can take only finite numbers of values
THE TERM CONTINUOUS SIGNAL AND DISCRETE SIGNAL CLASSIFY THE SIGNALS
ALONG THE TIME (i.e. horizontal axis) where as THE TERM ANALOG AND DIGITAL
SIGNAL CLASSIFY THE SIGNAL ALONG THE AMPLITUDE (i.e vertical axis)
The advantages of CMOS are as follows:
- Low power consumption
- It has a wider voltage variation 3v to 15vdc
- The fan-out capacity of this device is high
- high input resistance
Is a compressor the same thing as a inverter?
Inverter compressor is much better than digital scroll compressor, since it varies the speed of the motor in accordance with the load and thus saves energy when the load is less than maximum capacity. There is a misconception in the market that inverter technology gives you range or step based solution which is completely false, since there are inverter compressors made by companies like Danfoss, which can provide you with particular point based solution. There are harmonic filters which are provided along with the package as a solution to the minimal electromagnetic interference which might occur.
Precision cooling can be achieved by inverter compressors and also fast cooling can be achieved since the speed of the motor gets adjusted in fraction of a second, also the motor used is permanent magnet DC motor which causes further energy efficiency.Rather inverter technology compressors are the new generation compressors which will add new features to the range of air conditioning and refrigeration solutions provided, like: they will make it possible to obtain different temperatures in different rooms of a big house with one outdoor unit, based on the loads in the houses and the set point. They will make it possible to have multi compartment cold storage, where the same cold storage can be used to refrigerate various items likes potato and meat together etc.
Thus inverter compressors are innovation with the sustainability factor inbuilt as per the energy efficiency feature.
Difference between back EMF and induced EMF?
An induced electromotive force (emf) is an induced voltage. Voltage (emf) causes current flow, and this induced voltage will cause a current that is called the induced current.
We might also add that the induced current will cause a magnetic field to expand about the current path, and this field will "sweep" the conductor. The sweeping of the conductor by that expanding magnetic field will set up an emf that will oppose the emf that was creating it.
CommentTechnically, there is no such thing as an 'induced current'. It is voltage that is induced. Any current flows as a result of that induced voltage being applied to a load. But that current is certainly NOT induced!
How reactive power contributes to additional losses?
Reactive power is well known as that component which is shunted back and forth from the source to the load over the AC cycle. However, this does not mean the system has no reactive power losses. In fact they would be quite high. Loss is always measured with respect to load and not the source. When we term it reactive power loss, it is not the amount of power taken away from the source and not returned. That way, there would absolutely be no reactive loss at all because all the energy stored in the reactive elements are anyway returned. The idea is after all to provide the power to the load. So, the loss represents the amount of power unable to reach the load. The power lines are not purely resistive. They comprise considerable level of reactive elements especially line inductance.
Now, the active power which actually runs the load is never a separate entity. It co-exists with reactive power because the reactive (more so inductive) components of the load need to be energized in order to power the load. Reactive power loss is thus that amount of power which is deficient or 'not supplied' to the storage (reactive) elements of the load because of the reactive elements on the line. Thus the loss is always to be visualized in terms of load. That is why the complete return of reactive power to the source in the negative cycle has got nothing to do with loss understanding actually.
Hope this helps!
Why -48 Volts used in telecom equipments?
(i) Positive voltages cause comparatively more corrosion in metal than negative voltages. (ii) Negative voltages are safer for human body while doing Telecom activities. (iii) Lightning may cause positive voltages in the equipment circuitry. In that case, negative voltages (lack of electrons) neutralize positive charges and prevent excessive heat. (iv) Negative voltage is safer for long telephone line for transmitting power trough it. The reson for electing -48V in reference to ground is to avoid the nasty galvanic effects in telephone cabling. +48V would have nastier effect on wet cabling.
Why you use constant current source?
What follows below is not a full description. Full descriptions are in chapters of books about electronic power supplies.
A constant current source is an electronic device which acts as a source of power whereby, however the load resistance changes - within a certain fixed range - the device is designed to monitor the output current drawn from it and will change its output voltage to keep the output current constant within a certain fixed range.
Another answer
A constant current source will provide constant current with a load if the load changes the volts will change to compensate for the constant current flowing. Which is just opposite to a constant voltage source whereby a load change will change the current but not the voltage. And that how it works.
-- The current in each individual resistor is
(voltage across the whole circuit) divided by (the resistance of the individual resistor).
-- The current in any individual resistor is less than the total current in the circuit.
-- The total current in the circuit is the sum of the currents through each individual resistor.
How many watts amplifier can you use with 4 speakers that have 8 ohms each?
The question provides no info but here it is listening level is USUALLY 1w output for a normal room. speaker do come with an efficiency inheritance. the amplifier can be 1111w if you are carefully to set the level very low. amplifiers also come matched to the speaker impedance. This info only nobody should be able to answer your question.
In the unknown of measuring the voltage what should be the setting of VOM selector?
Use the highest available voltage setting. One should know the system voltage before attempting to measure, other wise it may lead to accidents.
If the resistance in a circuit is doubled while the voltage remains the constant the current is?
It is halved. coz voltage=current * resistance
What is the formula for finding resistance for a parallel series?
There is no such thing as a "parallel series".
The total effective resistance of many resistors in series is the sum of the
individual resistances. It's more than the greatest individual.
The total effective resistance of many resistors in parallel is the reciprocal of the
sum of the individual resistances' reciprocals. It's less than the smallest individual.
How do you determine capacitor's condition using multimeter for small capacitance?
You can use a multimeter to check the condition of a capacitor by using its highest range for measuring resistance. That range applies the highest voltage - often 9 volts - to the capacitor.
If the capacitor is of a polarized type - such as electrolytic - you must be sure to apply the multimeter's test leads to it the correct way round so as to apply the voltage in the right direction so that the capacitor can charge-up.
If the capacitor is shorted internally the multimeter will always show a low resistance.
If the capacitor is not shorted internally and is in good condition you will see a low resistance at first but, as it charges-up from the applied voltage, you should see the resistance rise in a steady manner until it registers near to infinity.
If the capacitor is failing the resistance will stay fairly low because the charge will not be held. If the capacitor is in good condition the charge should be held for several hours and the capacitor can be discharged (by shorting its wires) and then recharged repeatedly.
Warning Never ever try to test a capacitor whilst it is still connected into a circuit because: * it must always be discharged safely before you try to test it because you could receive a bad electrical shock if the capacitor is still holding a charge from being in-circuit. Wear rubber gloves on both hands and short its leads away from your eyes because, if it was holding a high voltage charge, there may be a big spark!
* other circuit components may get damaged, especially if they are semiconductors;
* other circuit components may prevent the capacitor from being charged-up.
How 555 timer is used to generate square wave?
The 8-pin 555 timer must be one of the most useful ICs ever made and it is used in many projects. With just a few external components it can be used to build many circuits, not all of them involve timing!
A popular version is the NE555 and this is suitable in most cases where a '555 timer' is specified. The 556 is a dual version of the 555 housed in a 14-pin package, the two timers (A and B) share the same power supply pins. The circuit diagrams on this page show a 555, but they could all be adapted to use one half of a 556.
Low power versions of the 555 are made, such as the ICM7555, but these should only be used when specified (to increase battery life) because their maximum output current of about 20mA (with a 9V supply) is too low for many standard 555 circuits. The ICM7555 has the same pin arrangement as a standard 555.
The circuit symbol for a 555 (and 556) is a box with the pins arranged to suit the circuit diagram: for example 555 pin 8 at the top for the +Vs supply, 555 pin 3 output on the right. Usually just the pin numbers are used and they are not labelled with their function.
The 555 and 556 can be used with a supply voltage (Vs) in the range 4.5 to 15V (18V absolute maximum).
Standard 555 and 556 ICs create a significant 'glitch' on the supply when their output changes state. This is rarely a problem in simple circuits with no other ICs, but in more complex circuits a smoothing capacitor (eg 100µF) should be connected across the +Vs and 0V supply near the 555 or 556.
Source: http://www.kpsec.freeuk.com/555timer.htm
How do you calculate or choose capacitor bank?
Normal power is the multiplication of current to combination of resistive and reactive or capacitive load. From the vector sum of Apparent power minus real power we can get reactive power(KVAr), which is basically lagging power due to reactive load. This will be the exact rating of capacitor bank. You can find it by cos $ of apparent power.
The metallic bonds which form the molecular structure of the metal solid are characterized by a virtually free flow of electrons between individual atoms, whereas non-metallic molecular bonds tend to keep the same electrons around each atom unless they are actively reacting. Consequently, when a source of electricity is applied to a metal, the free flow of electrons makes the conduction of charge, and in turn, electricity, much easier than it would be in a nonmetallic compound.
