Electronics Engineering

In earlier days of telephone networks, 48V DC was once found to be suitably high to be able to make telephone work on long telephone lines and still low enough not to cause serious danger if somebody touches the telephone wires. Telephone central offices (exchanges) so started using 48V DC. Even when newer automatic exhanges were setup, they were designed to make use of existing 48V battery sets and arrays which were available with telecom service providers. This legacy design practice has been continued and over many decades all new telecom devices have been designed to work with 48V.

The positive grounded or -48V system is also from telephone history. The negative voltage on the line was better than positive to prevent electro-chemical reactions from destroying the copper cable quickly, if cables get wet

Ans- It is because of cathodic protection. It reduces the sulphation on the battery terminals.

Ohm's Law: Current = Voltage divided by resistance

9 volts divided by 3 ohms = 3 amperes.

Improper handling can completely destroy (or severely damage, causing a delayed failure) many electronics components, without the person handling them becoming aware that anything had even happened at the time the part was destroyed (or severely damaged).

One main advantage is that it is easier, cheaper, and more efficient to battery back the system. -48V DC can be made simply of 4 12V batteries (think giant car batteries) in series. The string looks like this:

AC POWER --> RECTIFIER --> BATTERIES --> DC LOAD

To battery back an AC system you have this string.

AC POWER --> RECTIFIER --> BATTERIES --> INVERTER --> AC LOAD (which is usually converted back to DC by the equipment's power supply to run the electronics).

No step in this process is 100% efficient, and every part costs $$. DC eliminates a lot of these steps.

This is not to say that everything in a Central Office is DC powered -- they still have Air Conditioning, Lights, convenience outlets, etc -- but if you're ever in a Central Office when the power goes out, those things turn off until the generator kicks on and the transfer switch swings.

Also -- doing things with Low Voltage (-48V) does have some EXPENSIVE costs associated with it. COPPER power runs are very expensive because of the low voltage used (-48VDC) -- it takes more than twice as much copper to feed the same Wattage/Amperage as a 120V supply.

A=V*W

W=V/A

V=W/A

The simplest rating on a wire is how many A it can draw for how many feet (there are other ratings, such as maximum voltage, but most of these approach 600V, so don't apply to this comparison).

Most of these additional costs are one-time costs and therefore are justifiable.

It can depend on what you are slewing. Generally faster slewing means faster loading or unloading. E.g. if you are operating an excavator if the excavator can slew faster from you digging position to your loading position less time is needed to load a truck hence productivity is increased and cost reduced. For cranes it is a similar principle

IC 7402 is different from the other type of IC like 7404,7408,7432 and 7400 when it is connected to have an output desired... if you noticed all i mentioned ic is connected from left to the right.

input pin 1 and 2, output pin 3

input pin 4 and 5, output pin 6

input pin 13 and 12, output pin 11

input pin 10 and 9, output pin 8

while in nor gate, to have the desired output it must be connected from right to left...

input pin 2 and 3, output pin 1

input pin 5 and 6, output pin 4

input pin 8 and 9, output pin 10

input pin 11 and 12, output pin 13

The primary winding is the winding connected to the supply, while the secondary winding is the winding connected to the load. The terms, 'primary' and 'secondary' are unrelated to voltage levels.

you may find the answer from the periodic tables electron orbiting the nucleus is the answer

In general there is no direct advantage or disadvantage for either of the two technologies. There are various criterias that may result in an advantage for one of both in each specific design.

All items below have to be considered during the design of (a part of) a device:

* Is the electronic interfacing to analog or digital sensors / actuators / communication networks * What is the power budget * Is there a need for reconfiguring the design * What are the costs of the components

* What are the skills of the available developers? Are they hardware or software minded? * What are the data throughput requirements? Those questions do influence the design. If this question refers to an already made design, the following items are important:

* Digital systems which are processing analog data need to convert those signals. The conversion is the critical part. * Does the converter takes enough samples with a high enough resolution to be able to re-generate the original signal? * does the conversion use a lossy or loss-less compression technique? * Has the signal to be distributed over long distances, or to a lot of different places? Digital system easily integrate error detection and correction, where analog systems have more difficulties to do this. * Is a high quality required? You can see that it is strongly related to the target application, thus you have to make your own decision which is best in your situation. SPEED

You reduce ripple voltage by adding a low-pass filter. In the simplest case, you put a capacitor after the rectifier. The peak voltage will be the rectifier output voltage less the forward bias of the rectifier, while the minimum voltage will depend on current and capacitance. In a more complex case, you could use an LC filter, making the peak voltage smaller. Specifics are dependent on the power and performance requirements.

any diode if connected to where the anode is tie to a negative potential will block that voltage. Up to the limit of the breakdown potential of the diode whereby avalanche current will destroy the diode unless current limited

Light emitting diodes (LEDs) have advantages over incandescent bulbs. LEDs have longer service life, and are more efficient electrically. Better efficiency and life makes them environmentally friendly alternatives as a third advantage.

Yes, if you use two 4 ohm speakers or or one 4 ohm resistor and a 4 ohm speaker to equal the 8 ohm resistance per channel. An important thing to note about this, is that you will need to make sure you get a resistor that can handle the current. You can go higher in resistance but not lower, it must be equal to or higher. Something important is added: The amplifier will have an output impedance of around 0.04 ohms. In hi-fi we have always impedance bridging. Zout << Zin. The damping factor DF = Zin / Zout tells you what Zout is. Zout = Zin/DF. If the damping factor DF = 200 and the loudspeaker impedance is Zin = 8 ohms, the output impedance of the amplifier is Zout = 8 / 200 = 0.04 ohms. You see, there is no "8 ohm amplifier" with a 8 ohm output. Scroll down to related links and look at "Voltage Bridging - Zout << Zin".

They pass AC and block DC. So they are used in filters of various types as well as signal coupling. The capacitor is use to store the electric energy in the automobile ignition system. The capacitor is attached to the secondary winding of ignition coil. When contact breaker breaks the contact to the primary winding and sudden collapse of magnetic flux induces the high voltage to the secondary winding. This excess voltage is stored in capacitor. Capacitor releases the electric energy when it need. It protects cam and contact breaker points from corrosion or rusting.

wavenumber= 1/wavelength

a basic cable system works as follows information is received via satellite from the information providers also known as a channel in what is known as a head end where they process the signal and insert it into qualms which leave the head end on fiber optic cable by laser till it gets to the neighborhood or neighborhoods where there are subscribers. the fiber optics then hit what is called a node. at the node a fiber optical receiver changes it from light into db which is then sent out on distribution style coaxial cable usually a plastic based coating quantum reach style cable or qr cable. it then hits an amplifier where it is jumped up to about 40 db give or take as it travels down the street. where there is a house there is a tap in the qr cable, which is where the coaxial cable people are most familiar with starts

The Maximum Power Transfer Theorem is not so much a means of analysis as it is an aid to system design. The maximum amount of power will be dissipated by a load resistance when that load resistance is equal to the Thevenin/Norton resistance of the network supplying the power.

Seven Segment Display

emf is electromotive force

mmf is magnetic motive force

emf drives electon where as mmf drives magnetic field

generally open circuit test is performed on the low voltage side.....not on high voltage side.... becuase on low voltage side, we can apply that low voltage very easily ( i.e with a less amount of source is required)... whereas on high voltage side, we need a large power source in order to apply full voltage... in short circuit test, we will test on high voltage side by keeping Low voltage side being short circuit.because high voltage side needs less current source than low voltage side....

Since resistance is the ratio of voltage to current, if the voltage is constant then increasing the resistance will result in a reduction in current.

The basic elements in digital signal processing are an analog to digital converter, digital signal processor, and digital to analog converter. This process can take an analog input signal, convert it to digital for processing and offer an analog output.

Yes and no. Voltage is directly proportional to current from Ohm's Law (V=IR.) Thus, when voltage increases, so does current.

However, voltage can be inversely proportional to current in some situations. This can be seen in a transformer, where current and voltage are inversely proportional due to the law of conservation of energy, in which P(in) must equal P(out). Thus, a greater input voltage leads to a small output current.