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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
How do electric currents form?
The magnetic field means there is a charge surrounding a body.
Similarly if we move so much of charge (say electrons as in electricity) we can form a magnetic field.
These electrons if provide sufficient charge around a body magnetic field can easily be developed.
When a resistive AC circuit contains inductance the total opposition to current flow is called?
The resistance of an a.c. load is called 'resistance' (R). Resistance is not affected by frequency, only by the cross-sectional area, length, and resistivity of the conductor. Having said that, because of the skin effect, which causes an a.c. current to flow closer to the surface of the conductor, the effective cross-sectional are is reduced, so the value of a.c resistance is somewhat higher than the d.c. resistance -this difference increases with frequency.
The opposition to a.c due to inductive or capacitive loads is called reactance (inductive reactance or capacitive reactance), and the overall opposition to a.c. current is the vector sum of resistance and reactance, and is called impedance. That is:
(impedance)2 = (resistance)2 + (reactance)2
What are the causes of overheating of a dc motor?
a properly designed motor wont overheat unless it is overloaded
this is something like 3/4" drill with a 1/4" shaft that is used to drill in steel
sometimes hole saws have a 1/4" mandrel that will hold the entire line of saws
the motor must be matched to the load
What happens to the current as the resistor approches infinty?
Most resistors are linear, or 'ohmic', devices -which means that they obey Ohm's Law. So the ratio of voltage to current remains constant for variations in voltage. In other words, their resistance remains constant -providing their power rating isn't exceeded.
So you can say that, providing the current increase doesn't cause their power rating to be exceeded, their resistance should remain the same. Resistors wouldn't be of much use if their resistance value changed whenever the current through them changed!
Kirchhoff's Voltage and Current Laws apply to circuits: series, parallel, series-parallel, and complex.
If your circuit comprises just a single resistor, then they still apply. For example, the voltage drop across a single resistor will be equal and opposite the applied voltage (Kirchhoff's Voltage Law), and the current entering the resistor will be equal to the current leaving it (Kirchhoff's Current Law).
What are the bad reason for wind turbines?
Wind farms are bad because it can bring down value of peoples house when tryin to sell them. Wind farms also require a huge amount of space,make a tremendous amount of noise and can kill wildlife. Such as birds of flight, they can come tumbling down with one strike of lightning hitting those blades and that would mean a lot of work. Bird in flight can also damage the turbine and thy would mean passing over lots of money.
What are the industrial applications of multivibrator?
This circuit is the vital heart of all digital electronics, computers, pulse-code telephony and so on.
A multivibrator a.k.a. flip-flop, is a device which can settle in one of two stable states. They come in various flavours, single-shot or mono-stable, bi-stable. They are the basis of counting and time-code and so on.
That requires some detective work.
If you know where it is in a circuit, you might be able to figure out its function by context (seeing what it's connected to and what it might do).
You might be able to figure out the manufacturer by looking at subtle details of the package size and shape.
If you have the equipment, there are ways to disassemble and reverse engineer the chip and see the circuitry through a microscope to figure out its internal schematic.
Why don't ceramic capacitors have positive and negative terminals?
Normal Case:
Normally one will not find a polarity associated with a capacitor. Indeed, the quality of the manufacture would be put into question is the capacitor functions differently with different sign for the applied voltage.
Abnormal Case:
While common resistors are expected to function independent of polarity, it is possible to create resistors which are nonlinear and nonsymmetric in response to applied voltage. Just as diodes are nonsymmetric, one can imagine a diode-like material incorporated into the material of the capacity. There is no clear application for a nonsymmetric capacitor.
The only reason to label a capacitor as preferring one side positive over the other might be the effect of the rate of discharge is one of the charged surfaces is exposed to an environment which preferentially picks up or loses charge and there by affects performance.
What are the classification of amplifiers according to transistor configuration?
common emitter using fixed bias
How depletion region across zener diode gets thin?
A diode is basically a PN junction device. P type semiconductors are rich in holes while N types are rich in electrons. (Rich means majority carriers here, which are found in the outer shell of atoms).
Thus at the junction of this P and N type material, electrons and holes will combine resulting in a deficiency of charge carriers. This is termed the depletion region.
When you attach the negative terminal of a battery to the N end of the diode and the positive terminal to the P end, the electrons will be repelled towards the junction and holes too will move towards the junction region, making it thin (narrow) (Further increase in voltage will make current to pass through). The opposite occurs when they are connected the other way. The region becomes thin.
For normal operations, zener diodes are connected in reverse (diodes usually are connected reversely unless you want drop some voltage) the depletion layer widens, as described above. But at a certain reverse voltage, the zener starts to conduct suddenly. This is called avalanche/breakdown voltage. How the layer becomes thin (if at all, seems improbable) when they are reverse connected, I do not know.
Which battery last the longest is it DuracellEnergizerEveready or Rayovac?
yes it does i have done a experiment and energizer last longer that duracell
A torque multiplier increases the torque by increasing the length from which a bolt or nut is turned. This process is referred to as "mechanical advantage."
Inside a microwave oven,microwaves are made when electricity passes through a device called
Magnetron.Magnetron uses a strong magnet. The electricity and the magnet make microwave electromagnetic.
Why single crystal Silicon is used for IC fabrication?
pure silicon is easily available
cost is less
efficient fabrication techniques for silicon processing
better mechanical and physical properties of silicon
integration with control and signal processing circuitry
What is used to provide low voltage enrgy?
Assuming 24 volts or lower is implied in the question, low voltage energy can be taken from a battery or from a low-voltage transformer fed from the house supply.
Is antenna passive or active component?
An active antenna is an antenna which has an amplifier attached very closely to it. The antenna/amplifier system is called an active antenna. It is used for receiving signals only. The idea is to set the signal-to-noise ratio (SNR) before the signal travels along a transmission line where it is susceptible to interference and loss.
Is a pendulum a simple machine?
There are no moving parts, therefore it is not a machine. A chair is an object.
What is resistance of earthing electrode?
It's convenient to think of the earth electrode as being surrounded by a series of increasingly-larger 'shells' of soil, through which any earth-fault current will radiate outwards. The resistance of each 'shell' is inversely-proportional to its cross-sectional area. The shell immediately surrounding the earth electrode (1, in the following diagram) will have the smallest cross-sectional area and, therefore, the greatest resistance value; as we more further and further away from the earth electrode, each subseqent shell (2, 3, 4, etc.) increases in cross-sectional area and, therefore, reduces in resistance.
The further we move away from the earth electrode, the difference between the size of each shell becomes less and less significant and, therefore, the resistance between adjacent 'shells', will become less and less until, eventually, the increase in resistance, too, will become negligible.
The resistance of each of these 'shells' is, of course, cumulative. So, while the rate of change in resistance is greatest in the area immediately surrounding the earth electrode, the cumulative resistancecontinues to increase until it eventually become more-or-less constant. And it is this constant value that is taken as being the resistance of the earth electrode.
In practice, we cannot use an ordinary ohmmeter to measure the resistance of the earth electrode. Instead, the basis of the test is actually as follows.
A small spike is laid out in a straight line radiating away from the earth electrode. The resistance is then measured between the earth electrode and the spike, using an earth megger. The test is repeated several times, with the spike moved further and further away from the earth electrode. A graph drawn from the results shows a curve which is steepest (representing the greatest rate of change of resistance) where the test spike is closest to the earth electrode, and which eventually becomes horizontal (no further rate of change of resistance). The cumulative resistance increases, until there is no further significant increase in resistance, and this value is taken as the earth-electrode's resistance. The same results will be seen in whichever radial direction the resistance is measured, relative to the earth electrode. The area, immediately surrounding the earth electrode, in which the resistance value changes is termed its 'resistance area'.
For the UK, the wiring regulations, BS 7671:2008, specifies that the value of the earth-electrode resistance must be 'low enough to ensure that the potential of any exposed metalwork, with respect to earth, during an earth fault does not exceed 50 V for normal, dry, conditions'.
The 'On-Site Guide', a supplement to BS 7671:2008, further specifies (section 10.3.5) that the earth-electrode resistance should 'in any event, not exceed 200 Ω'.
How can you calibrate interface level transmitter?
First of all you have to know the gravities of the liquids you want to measure.
For example crude oil's gravity is 0.87 and water's gravity is 1.
A level transmitter uses 2 inlets, including the area of the level you want to observe.
You meter the distance (the height) between the two inlets.
CALIBRATION:
You fill the container with the heavier liquid, till the gravity's percent (%). Adjust for ZERO.
Fill till 100% to have the SPAN.
The gravity selector must be at the right position.
How to connect 4 - 6V batteries for -12V system?
In order to connect 4-6 volt batteries and end up with 12volts you will need to understand parallel and series connections. to connect two batteries in parallel you would connect the positive side of one battery to the positive side of the other battery; and the negative side of one battery to the negative of the other battery. doing this will not change the voltage. to connect in series you connect the positive of one battery to the negative of the other battery. doing this will increase the voltage;in this example you will end up with 12v. 6+6=12. when you stack batteries in a 2-cell flashlight that is connecting the batteries in series. The answer to the question is: connect two batteries in series; then connect the other two batteries in series. after this is done connect the two pairs of batteries in parallel. If you think of it visually you would have two batteries wide and two batteries tall.
What is the voltage of a circuit in a toaster with 12.0 amps of current and 8.0 ohms of resistance?
The formula you are looking for is Ohm's Law. Voltage = Current x Resistance (v = I x R). To solve for Current the formula is I = V/R.
What is the advantage of high level modulation over low level modulation?
Low level modulation: Class B (75%max) power amplifiers are used which offers better quality modulation i.e low distortion probability. Minimize generation of harmonics.
The advantage of using a linear RF LP amplifier is that the smaller early stages can be modulated, which only requires a small audio amplifier to drive the modulator.
High level modulation: Class C (90%max) power amplifiers are utilized which improves greatly the efficiency of the transmitter but low in quality i.e higher distortion level is expected.
A large audio amplifer will be needed for the modulation stage, at least equal to the power of the transmitter output itself. Traditionally the modulation is applied using an audio transformer, and this can be bulky. Direct coupling from the audio amplifier is also possible (known as a cascode arrangement), though this usually requires quite a high DC supply voltage (say 30V or more), which is not suitable for mobile units.
