Electronics Engineering

Increase, decrease, or remove the load

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Change the voltage and the current will also change in direct proportion, Ohms law.

This seems like a question from an electrical course, and is probably best answered by your course materials. It's your test question, not ours, and there won't always be someone to ask the answer of. Earn your diploma.

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Transistors are the fundamental building blocks of a computer, just as cells are the buildin blocks of any living organism. It is rare to find any individual transistors in a modern computer but every integrated circuit contains vast number of them. For example, every memory location will have a pair of trasistors, so there are 16 of them for each byte, so 16 million of them for each megabyte of memory. The central processor which carries out all the calculations and other processes also contains millions of transistors. As integrated circuits are developed, the size of each transistor gets smaller, so more can be packed into single chips but they are still doing the same job as the individual transistors that were used to build the very first solid state computers. To learn more about the way transistors operate in a computer, it is worth looking the way they are used to make simple logic gates. The basic gates such as OR, NOR, AND, NAND and various latches are used to create the powerful computers we take for granted today. A study of these gates will offer some insight into the way computers store, move and manipulate data using transistor technology.

• Can??? Sure, you'd just need to come up with a waterproof enclosure.

  But the problem is, many fluorescent fixtures don't work well when the temperature drops. Yes you can use fluorescent fixtures outside, they should be approved for the purpose and make sure they have 0 degree rated ballast for cold weather starting. The new electronic type ballast work in cold weather with no problems.

a dc ammeter is a ammeter which has three pins and it works by two wires.

Transistor is a three terminal device. Its shape may differ with applications.

Engineers often use 'models' to represent the behaviour of complicated devices such as machines. In the case of transformers, these 'models' are more-usually called 'equivalent circuits' -schematic diagrams, using simple resistors and inductors, to simulate the operation of the transformer, and to help us construct the transformer's phasor diagrams.

The simplest equivalent circuit, which can be considered a 'first approximation' of the transformer's behavioiur, is commonly called an 'ideal transformer', and only accounts for the transformer's ability to step up or step down the primary voltage and secondary current.

The 'second approximation' equivalent circuit, takes into account the core losses and magnetising current.

The 'third approximation' equivalent circuit takes into account the resistance and leakage reactance of the primary and secondary circuits, responsible for the regulation of the transformer, and it takes into account both the core losses and the copper losses. The 'third approximation' equivalent circuit, therefore, can be considered the most accurate equivalent circuit.

When you convert digital signal to analog, it is called as an analog signal.

The device used is called digital to analog converter.

depend on the R value(s) because V Source = Sum of individual voltage across each R in the series so if R in the series are equal value, then their V are the same and their V total will be equal of the V Source

it is used in voice transmission,to active vibration control and is used in channel vocoder

It already is in theory.

If you consider what you're asking, if it is an image and not a Photograph then what it ultimately is, is a set of 1s and 0s defining bits and bytes and on and off. Therefore meaning the moment it touches the computer it is an electrical signal.

are called dopants

Once an SCR has been turned on by means of a gate pulse, it latches, or remains on. The only way to turn the SCR off is to either remove the anode to cathode voltage, remove the load current (SCR's have a minimum current below which they will not fire), or reverse bias the SCR. If the SCR is used in an AC circuit, turn off is easy. This is because the voltage falls to zero, then reverse biases the SCR every cycle. This naturally turns off the SCR. In fact, you have to re-trigger the gate every cycle to turn it back on. In a DC circuit, the SCR must be reset by some means as mentioned above. Once the SCR fires, there is nothing you can do to the gate to control the device. The gate only turns it on, not off. There is a similar device, called a GTO, or gate-turn-off device, that can be turned off via the gate. Once an SCR is on it will not turn -off unless the minimum holding current is met. that can be accomplished by reversing anode polarity or by decreasing loading to below holding current

It is called an open, incomplete, or broken circuit. Circuits might be opened intentionally (using a switch), or unintentionally (breaks in, or disconnected wiring).

s for static

Sure, check the solar power sites for info. You can run most ac appliances by solar, wind, hydro etc. via an inverter if you have a system sufficient to keep up with the load requirements.

Because higher voltage can carry further.

That answer is too simplistic. The actual reason is as follows: for any given load, the higher the supply voltage, the lower the resulting current. Lower currents mean smaller diameter transmission/distribution conductors can be used and the line losses(I2R) are lower.

It is used for various instruction set and interrupt systems also.

They were a popular, early, microprocessor commonly embedded in washing machines and domestic appliances, to replace mechanical timers and interlocks.

sir,please tell us about microcontroller 8951 program for robotic car

The charge in this case is simply the current multiplied by the time.

The charge in this case is simply the current multiplied by the time.

The charge in this case is simply the current multiplied by the time.

The charge in this case is simply the current multiplied by the time.

Conventional VOR

A conventional VOR (CVOR) has three Amplitude Modulated (AM) signals encoded on a VHF carrier:

1) a 30 Hz variable (VAR), which is modulated by the antenna, not the transmitter;

2) a 9960 Hz subcarrier, which is in turn frequency modulated (FM) with a 30 Hz reference (REF) signal;

3) and a voice / identifier channel, which includes 1020 Hz "Morse code" identifiers and aural voice signals.

The CVOR antenna is a slightly directional antenna, which means it works best in one direction and worst in the opposite direction. This antenna is physically rotated clockwise at 1800 rpm (30 Hz).

Imagine one observer (receiver) on a line that is magnetically North of the VOR and another observer on the line that is magnetically East of the VOR. Suppose the VOR station transmits a constant amplitude carrier (in reality, the VOR carrier amplitude isn't exactly constant). The VOR carrier is fed to the spinning antenna. The observers see the VOR carrier increase in amplitude when to antenna is pointed toward the observer (peak) and decrease when the antenna points in the opposite direction (valley). Since the antenna rotates 30 revolutions per second, the observer sees 30 peaks and valleys in the carrier amplitude, the carrier is amplitude modulated with a 30 Hz signal. The phase of the 30 Hz modulating signals perceived by the two observers in our example differ by 90 degrees (North observer sees peak 90 degrees before East observer sees peak). Since this signal's phase varies with position relative to the VOR, the signal is called the variable channel (VAR).

In order for the VAR channel to be useful, we need a reference 30 Hz signal (REF). This signal must be perceived by all observers as the same phase, regardless of position relative to the VOR. Here is the problem: the VAR 30 Hz signal is already modulated on the carrier. If the REF 30 Hz signal is modulated onto the carrier without processing, a receiver would find two 30 Hz signals (just one signal if REF and VAR signals are in phase). How would the receiver know which signal is the REF and which is the VAR?

To get around this problem, the VOR takes a 9960 Hz carrier and frequency modulates this carrier with the REF 30 Hz signal. The modulation index is 15, meaning the 9960 carrier has a deviation of 450 Hz (30 Hz times 15). In other words, the subcarrier varies between 9510 Hz to 10410 Hz (9960 +&- 450 Hz). This frequency excursion occurs 30 times per second (30 Hz). The subcarrier signal spectrum does not overlap with the spectra of the VAR or aural signal; therefor it can be amplitude modulated on the RF carrier.

The reason for frequency modulation of the REF signal on the 9960 carrier, as opposed to amplitude modulating the REF signal, is that the AM detector in a VOR receiver would still output two 30 Hz ambiguous signals and a 9960 signal, all summed together.

The VOR receiver has an AM detector which recovers the VAR, 9960 Hz subcarrier, and aural information (called the VOR composite video signal (COMP)) from the RF carrier. The VOR instrumentation processor takes the detected VOR signal , and processes the signal as follows:

1) COMP is processed through a low pass filter that preserves 30 Hz to get the VAR signal;

2) COMP is processed through a high pass filter to reject the VAR and aural signals, then an amplitude limiter, and then though an FM detector to get the REF signal. The FM detector could be a discriminator (used in the bad old days), or a phase lock loop (used in modern equipment);

3) COMP is not processed by VOR instrumentation; however it may be filtered to please the listener, i.e. range filter (1020 Hz bandpass), voice filter (200 to 3000 Hz bandpass).

VOR bearing (magnetic direction away from the VOR) is simply the phase angle of the VAR signal minus the phase angle of the REF signal.

Doppler VOR

The difference between Doppler VOR (DVOR) and CVOR is in the method of encoding the VAR signal on the VOR carrier. The REF and aural channels are the same for both VOR types.

To understand DVOR, one must understand the Doppler effect. The classic example is of a stationary observer standing near (not on) a railroad track. The train's horn (source) is moving at a positive velocity toward the observer. The observer hears the horn at a higher pitch than some one on the train hears. As the train passes, the observer on the ground hears the horn at a lower frequency than the person on the train because the velocity of the horn is negative (moving away from the ground observer). This is an example of Doppler effect for pressure (sound) waves.

Doppler also applies to radio waves (and light for that matter). To understand how DVOR works, here is a ridiculous illustration: suppose a complete CVOR station, except with a non-spinning omnidirectional antenna (antenna works the same in all directions) is placed on a rail car. The rail car is on a circular track with a diameter of approximately 13.4 meters. The rail car runs really fast: 30 laps per second! (I told you the example is ridiculous.)

An observer some distance away from the moving VOR will observe the VOR carrier frequency increase as the rail car comes toward the observer and a decrease as the rail car move away. Since the VOR comes and goes 30 times per second, the carrier frequency is frequency modulated by a 30 Hz carrier. Moving a VOR around a track at a tangential velocity of 1260 meters per second isn't practical. The way a DVOR "moves" the VOR is to have an array of evenly spaced omnidirectional antennas mounted on the 13.4 meter diameter circle. The number of antennas can be as many as 48. Except for "make-before-break" overlaps, only one antenna is connected to the transmitter at any given instant. Each antenna in the array is activated one at a time, in sequence (next antenna on the circle). If the number of antennas in the array is 48, each antenna will be on for 7.5 degrees of 30 Hz (694.4 microseconds). Less expensive systems would use fewer antennas, and each antenna would be on for a longer period of time. The 48 antenna array would require a 48 throw rotatry switch, that can be switched electronically or by a synchronous motor. Each antenna would have to be fed by a transmission line that is the same length as the other antennas. It is important to understand that the VAR signal is encoded by the time-domain spacial velocity of the signal caused by switching individual antennas. It would be a mistake to believe the other antennas are used as a phase array to make a rotatable directional antenna. If the antenna "rotates", the VAR signal is amplitude modulated; therefore a CVOR. If the antenna "moves" spatially in time, the VAR signal is frequency modulated; therefor a DVOR.

Does it take a different VOR receiver to process DVOR? No, a VOR receiver does not "care" if it receives DVOR or CVOR. The spectrum of the CVOR REF signal is a narrow signal at the RF carrier frequency (fc) (between 108 to 117.95 MHz), and two side bands, one at fc + 30 Hz and the other at fc - 30 Hz. The DVOR REF signal has the same spectrum components as the CVOR REF signal, with the addition of sidebands at (plus and minus) 60 Hz, 90 Hz, 120 Hz ... and on (with diminishing in amplitudes). The VOR receiver does not react to the sidebands at 60 Hz and above because the VAR signal is separated by a low pass filter. After this low pass filtering, the spectra of the CVOR and DVOR VAR signals are the same.

Your question is better expressed as why can an ac circuit be shorted to earth when a dc circuit can't be? With an ac supply only the positive feed is actually present at the socket. There is no negative, just a neutral return which is actually connected to earth at the power station / substation. Earthing an ac curcuit just provides a shorter route to the earth, which is where it would have gone anyway. The earth connection at the socket is just to provide a safe means of dumping the current locally in the event of a fault. In a dc circuit the current has nowhere to go, other than to the negative terminal / rail. Without both positive and negative being present no circuit can be formed.