Electronics Engineering

The true advantage of digital wattmeters over electromechnical wattmeters is the cost to operate the meter. Also, virtually all digital meters can emitt a radio signal to forward the power useage for a certain time period to a recording device. This means that a utility can drive around the block rather than manually walking up to each house and recording the power usage every month. The best electromechanical wattmeter has a power consumption of 24Watts. The leading Centron digital meter has a starting power of less than 5Watts. The operating power consumption for electromechanical meters is also more than that of digial meters. Loss of electromechanical meters is ~ .7Watts Loss of digital meters ~.5Watts The display could be considered an advantage also because people who are not trained in reading a scaled meter can read a digital meter easily, however, if they aren't trained in reading a meter they most likely will not understand what they are reading anyway.

Phase-shift oscillator

Armstrong oscillator

Cross-coupled LC oscillator

RC oscillator

As with all things, temperature does change things.

With amplifiers, the changing temperature in the power transistors running the speakers can become a ruining experience.

The louder you play, the more heat is generated in these transistors.

The hotter they get, the less current do they stand.

Some transistors may be able to push forward 160-200 Watts of music at 25 degrees Celsius. As they get warmer, their level of 'performance' must be put down according to temperature. At 50 degrees Celsius, they may be able to withstand 120 Watts of music. at 100 degrees, they may only be able to give 60 watts of music. At 120 degrees, they are close to the transistors internal breakdown temperature and only 10 watts of music may be destructive.

Good cooling of power transistors in amplifiers help avoid destroying an amplifier but it does not fully solve the problem of temperature drift.

A mayor issue is that an amplifier that does not consume power (like when no music is played) will not be able to start instantaneously to play good music. We will experience a delayed action that is very well audible. In a class B or a class AB amplifier, this is fixed by always having the amplifier to work, they just work on making silence, constantly having a small current over the power transistors.

This small current however is dangerous for the transistors. The transistors try to 'amplify' and in this process, all of this current is transformed into heat. The big problem is that as transistors get warmer, their ability to amplify increases.

A small current of 25 mA may generate 2 Watt of heat at 25 Degrees Celsius, but at 75 Degrees Celsius, the same small current of 25 mA may generate 20 Watt of heat. The process is self destructive. As transistors heat up, they generate more and more heat and get more and more out of the little start current of 25 mA. In the end, they burn up internally.

It is important that the small current decreases with the increase of temperature, otherwise your amplifier will quickly be destroyed. This can happen in a matter of minutes only, even with quite a decent cooling profile and even a fan attached.

In a series circuit, if you open a bulb, current loop will be broken. So, current cannot travel all the wayback, hence no output. But in a parallel circuit, current will be only shared with parallel circuit, but the loop remains closed even if you remove the bulb. So, no change occurs.

PN means pressure rating of a pipe....PN is just a symbolic representation....

When a circuit is in off condition then it is called an open circuit..

FET is abbreviation of Field Effect Transistor. This is a transistor in which current is controlled by voltage only and no current is drawn. It is a high input impedence device and is used in computers, telecommunication and control circuits. This transistor is better in certain parameters as compared to BJT, that is Bipolar Junction Transistor.

The Quickest easiest way is going to be with a battery or jumper pack. Ground the body and touch the two terminals one at a time with the positive lead from a battery or jumper pack. One makes it turn the other makes it stop, the one that makes it turn is the starter or armature, the one that does nothing is the field. To go one step further to see if you are getting a good generator start it to full rpm and remove from the armature terminal and quickly touch the field terminal if the charging part is working correctly it should forcibly stop the pulley from rotating, you will notice a difference from just letting it spin to a stop.

The 555 timer is commonly used in IC electronics and in electronic circuits. In the monostable multivibrabor mode, the 555 works as a pulse generator. In astable mulitvibrator mode, the 555 is free running, and goes back and forth between frequencies.

EHV and VHV substations tend to have a signature hum; this is due to small electrical arcs. This is normal. Most of the time this will not be audible on VHV and EHV power lines. If you are hearing this from the power line, it could be bad and the utility may want to know. It shouldn't be a risk to you, however the hum may be resulting from arcing, which can be fairly high frequency, which can mess with electronics's signals such as cell phones and radio (won't damage them, just bad reception).

The formula you are looking for is I = W/E. Amps = Watts/Volts.

To get Watts you multiply Amps x Volts. So in your case you just do some reverse math and divide the Watts by the volts and you get your amperage.

so 100/120=0.83 Amps

I think it is to determine how powerful you have to make your power supply to run the current demand load continously with a margin for error on the plus side. A 12 volt car battery has a low load resistance and needs some heafty components in a battery charger. A charger (or supply) for a 12 volt boom box with a high load resistance may be the size of a small paper cup. They both supply 12-15 volts but the load resistance is very much different E=IR I=E/r R=E/i

No way of telling. to get amps you have to have a current flow, which you get when you connect a consumer to an outlet. Then the consumer will pull amps according to its wattage rating (Watts / Volts = amps) - assuming it's all hooked to a fuse with enough rating.

flux acts as a wetting agent in the soldering process, reducing the surface tension of the molten solder and causing it to better wet out the parts to be joined.

The 555 timer IC is a device that can create various kinds of time delays in a circuit. It uses a threshold pin that is typically connected to an RC circuit. Depending on how it is connected, it can operate in one shot mode (monostable), astable mode (retriggerable), or schmitt trigger mode.

Current is defined to be a flow of electrically charged carriers. These are usually electrons or electron-deficient atoms. It is symbolized by uppercase letter I.

The invention of the capacitor varies somewhat depending on who you ask. There are records that indicate a German scientist named Ewald Georg von Kleist invented the capacitor in November 1745. Several months later Pieter van Musschenbroek, a Dutch professor at the University of Leyden came up with a very similar device in the form of the Leyden jar, which is typically credited as the first capacitor. Since Kleist didn't have detailed records and notes, nor the notoriety of his Dutch counterpart, he's often overlooked as a contributor to the capacitor's evolution. However, over the years, both have been given equal credit as it was established that their research was independent of each other and merely a scientific coincidence.

The Leyden jar was a very simple device. It consisted of a glass jar, half filled with water and lined inside and out with metal foil. The glass acted as the dielectric, although it was thought for a time that water was the key ingredient. There was usually a metal wire or chain driven through a cork in the top of the jar. The chain was then hooked to something that would deliver a charge, most likely a hand-cranked static generator. Once delivered, the jar would hold two equal but opposite charges in equilibrium until they were connected with a wire, producing a slight spark or shock .

Benjamin Franklin worked with the Leyden jar in his experiments with electricity and soon found that a flat piece of glass worked as well as the jar model, prompting him to develop the flat capacitor, or Franklin square. Years later, English chemist Michael Faraday would pioneer the first practical applications for the capacitor in trying to store unused electrons from his experiments. This led to the first usable capacitor, made from large oil barrels. Faraday's progress with capacitors is what eventually enabled us to deliver electric power over great distances. As a result of Faraday's achievements in the field of electricity, the unit of measurement for capacitors, or capacitance, became known as the farad.

Its used in collector amplitude modulation,Radio frequency recievers ..etc

reactance and resistance are both measured in ohms because both are opposition to current flow. the only difference is resistance is the real component while reactance is the imaginary component.

the motor should only rotate in a rated speed,if the speed is more than rated speed then the motor will be damaged........to control the speed of motor a rheostat should be connected to the field side of motor......by variying the rheostat we can control the speed of motor......

Coulomb is a measure of electric charge:
One coulomb is the amount of electric charge transported in one second by a steady current of one ampere.

http://en.wikipedia.org/wiki/Coulomb

The section we call 'radio'.

Of course, there's no end to the electromagnetic spectrum, at least not on the

low-frequency end, so there's really no such thing as "greatest" wavelength.

As frequencies go down past radio and below, wavelength just keeps getting

longer ... the bit of radiation from the 60 Hz utility power lines has a wavelength

of almost 5,000 kilometers ( ! ! ). But we don't use anything down there in the

form of radiation ... antennas would need to be gigantic in order to be the least

bit efficient ... so there's no popular name for the radiated form.

The 'generic' answer to the question is: The type with the lowest frequency.