Electrical Engineering

Don't stick anything into a plug socket unless it is a plug, this doe not include fingers, pencils or scissors.

Do not use wet hands when turning on electrical equipment.

Ensure that the plug has the correct fuse rating for the appliance.

Ensure that if the appliance needs to be earthed then it is.

Ensure that theg.

Always turn off the plug sockets when a plug is not in it otherwise your house will be swamped by delta wave radiation.

Don't stick anything into a plug socket unless it is a plug, this doe not include fingers, pencils or scissors.

Do not use wet hands when turning on electrical equipment.

Ensure that the plug has the correct fuse rating for the appliance.

Ensure that if the appliance needs to be earthed then it is.

Ensure that the fuse box has the correct rating for the power requirements of the building.

Always turn off the plug sockets when a plug is not in it otherwise your house will be swamped by delta wave radiation.

The reduction of voltage or the increase of resistance will reduce the current in a circuit.

I=kw*1000/E*1.732 primary side 90.3 amp. Secondary side 208 amp. 100 amp 277-480 breaker good for primary side usually i install 200 amp 208-110 secondary side. Primary wire size #2 secondary side 3/0

A wind chime has several objects which produce a "chime" when they strike each other. When a wind chime is left hanging freely, the wind makes the objects move and they strike each other to produce a chiming sound.

A thyristor is a type of semi-conductor and is used in a circuit to control the application of electrical power to a load. They are often found as the switching element in light dimmers and can be used as control elements in power supplies (variable or regulated).

Types of thyristors are diacs, triacs, sidacs and SCRs (silicon controlled rectifier).

Think of electricity as water in a pipe. The larger the pipe the more water can flow thru. That is current = volume = amperage = amount of heat. Voltage can be compared to pressure in a pipe. That is drive/force. Most welding machines allow you to control the amperage but not the voltage.

The most common system you will see is in the form:

"xx/y [type] [/w ground]" * xx is the wire size in the AWG system * y is the number of conductors. * Type THHN (for example) is the kind of wire insualtion. Romex (which is a brand name) is the regular plastic sheathed cable used 90% of the time in homes and commercial buidlings. * BX is metal sheathed cable. * /w ground means the cable has a ground wire.

* XX, the size, tells you how much current can flow through the wire, this is the primary consideration when choosing wire. * The voltage rating is also included. (typ 600V) meaning it is suitable for circuits up to 600V. * THHN, THXN, XHHW, etc, is the type of insulation. There are many of these for industrial wiring & should only be a concern if your wiring is outdoors, or installed in non typical environments.

* You will also see a temperature rating stamped in Deg C, 60, 75, & 90. This tells you the operating conditions under which the cable is suitable. Keep in mind that resistivity rises with temperature, so the hotter the area, the lower ampacity. Follow the link for further explanation.

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Many of these disciplines overlap with other engineering branches, spanning a huge number of specializations including hardware engineering, power electronics, electromagnetics and waves, microwave engineering, nanotechnology, electrochemistry, renewable energies, mechatronics, and electrical materials science.Electrical engineers typically hold a degree in electrical engineering or electronic engineering. Practising engineers may have professional certification and be members of a professional body or an international standards organization. These include the International Electrotechnical Commission (IEC), the Institute of Electrical and Electronics Engineers (IEEE) and the Institution of Engineering and Technology (IET) (formerly the IEE). Electrical engineers work in a very wide range of industries and the skills required are likewise variable. These range from circuit theory to the management skills of a project manager. The tools and equipment that an individual engineer may need are similarly variable, ranging from a simple voltmeter to sophisticated design and manufacturing software. Electricity has been a subject of scientific interest since at least the early 17th century. William Gilbert was a prominent early electrical scientist, and was the first to draw a clear distinction between magnetism and static electricity. He is credited with establishing the term "electricity". He also designed the versorium: a device that detects the presence of statically charged objects. In 1762 Swedish professor Johan Wilcke invented a device later named electrophorus that produced a static electric charge. By 1800 Alessandro Volta had developed the voltaic pile, a forerunner of the electric battery. In the 19th century, research into the subject started to intensify. Notable developments in this century include the work of Hans Christian Ørsted who discovered in 1820 that an electric current produces a magnetic field that will deflect a compass needle, of William Sturgeon who, in 1825 invented the electromagnet, of Joseph Henry and Edward Davy who invented the electrical relay in 1835, of Georg Ohm, who in 1827 quantified the relationship between the electric current and potential difference in a conductor, of Michael Faraday (the discoverer of electromagnetic induction in 1831), and of James Clerk Maxwell, who in 1873 published a unified theory of electricity and magnetism in his treatise Electricity and Magnetism.In 1782 Georges-Louis Le Sage developed and presented in Berlin probably the world's first form of electric telegraphy, using 24 different wires, one for each letter of the alphabet. This telegraph connected two rooms. It was an electrostatic telegraph that moved gold leaf through electrical conduction. In 1795, Francisco Salva Campillo proposed an electrostatic telegraph system. Between 1803–1804, he worked on electrical telegraphy and in 1804, he presented his report at the Royal Academy of Natural Sciences and Arts of Barcelona. Salva's electrolyte telegraph system was very innovative though it was greatly influenced by and based upon two new discoveries made in Europe in 1800 – Alessandro Volta's electric battery for generating an electric current and William Nicholson and Anthony Carlyle's electrolysis of water. Electrical telegraphy may be considered the first example of electrical engineering. Electrical engineering became a profession in the later 19th century. Practitioners had created a global electric telegraph network, and the first professional electrical engineering institutions were founded in the UK and USA to support the new discipline. Francis Ronalds created an electric telegraph system in 1816 and documented his vision of how the world could be transformed by electricity. Over 50 years later, he joined the new Society of Telegraph Engineers (soon to be renamed the Institution of Electrical Engineers) where he was regarded by other members as the first of their cohort. By the end of the 19th century, the world had been forever changed by the rapid communication made possible by the engineering development of land-lines, submarine cables, and, from about 1890, wireless telegraphy. Practical applications and advances in such fields created an increasing need for standardised units of measure. They led to the international standardization of the units volt, ampere, coulomb, ohm, farad, and henry. This was achieved at an international conference in Chicago in 1893. The publication of these standards formed the basis of future advances in standardisation in various industries, and in many countries, the definitions were immediately recognized in relevant legislation.During these years, the study of electricity was largely considered to be a subfield of physics since the early electrical technology was considered electromechanical in nature. The Technische Universität Darmstadt founded the world's first department of electrical engineering in 1882 and introduced the first degree course in electrical engineering in 1883. The first electrical engineering degree program in the United States was started at Massachusetts Institute of Technology (MIT) in the physics department under Professor Charles Cross, though it was Cornell University to produce the world's first electrical engineering graduates in 1885. The first course in electrical engineering was taught in 1883 in Cornell's Sibley College of Mechanical Engineering and Mechanic Arts. It was not until about 1885 that Cornell President Andrew Dickson White established the first Department of Electrical Engineering in the United States. In the same year, University College London founded the first chair of electrical engineering in Great Britain. Professor Mendell P. Weinbach at University of Missouri soon followed suit by establishing the electrical engineering department in 1886. Afterwards, universities and institutes of technology gradually started to offer electrical engineering programs to their students all over the world. During these decades use of electrical engineering increased dramatically. In 1882, Thomas Edison switched on the world's first large-scale electric power network that provided 110 volts — direct current (DC) — to 59 customers on Manhattan Island in New York City. In 1884, Sir Charles Parsons invented the steam turbine allowing for more efficient electric power generation. Alternating current, with its ability to transmit power more efficiently over long distances via the use of transformers, developed rapidly in the 1880s and 1890s with transformer designs by Károly Zipernowsky, Ottó Bláthy and Miksa Déri (later called ZBD transformers), Lucien Gaulard, John Dixon Gibbs and William Stanley, Jr.. Practical AC motor designs including induction motors were independently invented by Galileo Ferraris and Nikola Tesla and further developed into a practical three-phase form by Mikhail Dolivo-Dobrovolsky and Charles Eugene Lancelot Brown. Charles Steinmetz and Oliver Heaviside contributed to the theoretical basis of alternating current engineering. The spread in the use of AC set off in the United States what has been called the war of the currents between a George Westinghouse backed AC system and a Thomas Edison backed DC power system, with AC being adopted as the overall standard. During the development of radio, many scientists and inventors contributed to radio technology and electronics. The mathematical work of James Clerk Maxwell during the 1850s had shown the relationship of different forms of electromagnetic radiation including the possibility of invisible airborne waves (later called "radio waves"). In his classic physics experiments of 1888, Heinrich Hertz proved Maxwell's theory by transmitting radio waves with a spark-gap transmitter, and detected them by using simple electrical devices. Other physicists experimented with these new waves and in the process developed devices for transmitting and detecting them. In 1895, Guglielmo Marconi began work on a way to adapt the known methods of transmitting and detecting these "Hertzian waves" into a purpose built commercial wireless telegraphic system. Early on, he sent wireless signals over a distance of one and a half miles. In December 1901, he sent wireless waves that were not affected by the curvature of the Earth. Marconi later transmitted the wireless signals across the Atlantic between Poldhu, Cornwall, and St. John's, Newfoundland, a distance of 2,100 miles (3,400 km).Millimetre wave communication was first investigated by Jagadish Chandra Bose during 1894–1896, when he reached an extremely high frequency of up to 60 GHz in his experiments. He also introduced the use of semiconductor junctions to detect radio waves, when he patented the radio crystal detector in 1901.In 1897, Karl Ferdinand Braun introduced the cathode ray tube as part of an oscilloscope, a crucial enabling technology for electronic television. John Fleming invented the first radio tube, the diode, in 1904. Two years later, Robert von Lieben and Lee De Forest independently developed the amplifier tube, called the triode.In 1920, Albert Hull developed the magnetron which would eventually lead to the development of the microwave oven in 1946 by Percy Spencer. In 1934, the British military began to make strides toward radar (which also uses the magnetron) under the direction of Dr Wimperis, culminating in the operation of the first radar station at Bawdsey in August 1936.In 1941, Konrad Zuse presented the Z3, the world's first fully functional and programmable computer using electromechanical parts. In 1943, Tommy Flowers designed and built the Colossus, the world's first fully functional, electronic, digital and programmable computer. In 1946, the ENIAC (Electronic Numerical Integrator and Computer) of John Presper Eckert and John Mauchly followed, beginning the computing era. The arithmetic performance of these machines allowed engineers to develop completely new technologies and achieve new objectives.In 1948 Claude Shannon publishes "A Mathematical Theory of Communication" which mathematically describes the passage of information with uncertainty (electrical noise). The first working transistor was a point-contact transistor invented by John Bardeen and Walter Houser Brattain while working under William Shockley at the Bell Telephone Laboratories (BTL) in 1947. They then invented the bipolar junction transistor in 1948. While early junction transistors were relatively bulky devices that were difficult to manufacture on a mass-production basis, they opened the door for more compact devices.The surface passivation process, which electrically stabilized silicon surfaces via thermal oxidation, was developed by Mohamed M. Atalla at BTL in 1957. This led to the development of the monolithic integrated circuit chip. The first integrated circuits were the hybrid integrated circuit invented by Jack Kilby at Texas Instruments in 1958 and the monolithic integrated circuit chip invented by Robert Noyce at Fairchild Semiconductor in 1959.The MOSFET (metal-oxide-semiconductor field-effect transistor, or MOS transistor) was invented by Mohamed Atalla and Dawon Kahng at BTL in 1959. It was the first truly compact transistor that could be miniaturised and mass-produced for a wide range of uses. It revolutionized the electronics industry, becoming the most widely used electronic device in the world. The MOSFET is the basic element in most modern electronic equipment, and has been central to the electronics revolution, the microelectronics revolution, and the Digital Revolution. The MOSFET has thus been credited as the birth of modern electronics, and possibly the most important invention in electronics.The MOSFET made it possible to build high-density integrated circuit chips. Atalla first proposed the concept of the MOS integrated circuit (MOS IC) chip in 1960, followed by Kahng in 1961. The earliest experimental MOS IC chip to be fabricated was built by Fred Heiman and Steven Hofstein at RCA Laboratories in 1962. MOS technology enabled Moore's law, the doubling of transistors on an IC chip every two years, predicted by Gordon Moore in 1965. Silicon-gate MOS technology was developed by Federico Faggin at Fairchild in 1968. Since then, the MOSFET has been the basic building block of modern electronics. The mass-production of silicon MOSFETs and MOS integrated circuit chips, along with continuous MOSFET scaling miniaturization at an exponential pace (as predicted by Moore's law), has since led to revolutionary changes in technology, economy, culture and thinking.The Apollo program which culminated in landing astronauts on the Moon with Apollo 11 in 1969 was enabled by NASA's adoption of advances in semiconductor electronic technology, including MOSFETs in the Interplanetary Monitoring Platform (IMP) and silicon integrated circuit chips in the Apollo Guidance Computer (AGC).The development of MOS integrated circuit technology in the 1960s led to the invention of the microprocessor in the early 1970s. The first single-chip microprocessor was the Intel 4004, released in 1971. It began with the "Busicom Project" as Masatoshi Shima's three-chip CPU design in 1968, before Sharp's Tadashi Sasaki conceived of a single-chip CPU design, which he discussed with Busicom and Intel in 1968. The Intel 4004 was then designed and realized by Federico Faggin at Intel with his silicon-gate MOS technology, along with Intel's Marcian Hoff and Stanley Mazor and Busicom's Masatoshi Shima. The microprocessor led to the development of microcomputers and personal computers, and the microcomputer revolution. Electrical engineering has many subdisciplines, the most common of which are listed below. Although there are electrical engineers who focus exclusively on one of these subdisciplines, many deal with a combination of them. Sometimes certain fields, such as electronic engineering and computer engineering, are considered separate disciplines in their own right. Power engineering deals with the generation, transmission, and distribution of electricity as well as the design of a range of related devices. These include transformers, electric generators, electric motors, high voltage engineering, and power electronics. In many regions of the world, governments maintain an electrical network called a power grid that connects a variety of generators together with users of their energy. Users purchase electrical energy from the grid, avoiding the costly exercise of having to generate their own. Power engineers may work on the design and maintenance of the power grid as well as the power systems that connect to it. Such systems are called on-grid power systems and may supply the grid with additional power, draw power from the grid, or do both. Power engineers may also work on systems that do not connect to the grid, called off-grid power systems, which in some cases are preferable to on-grid systems. The future includes Satellite controlled power systems, with feedback in real time to prevent power surges and prevent blackouts. Control engineering focuses on the modeling of a diverse range of dynamic systems and the design of controllers that will cause these systems to behave in the desired manner. To implement such controllers, electrical engineers may use electronic circuits, digital signal processors, microcontrollers, and programmable logic controllers (PLCs). Control engineering has a wide range of applications from the flight and propulsion systems of commercial airliners to the cruise control present in many modern automobiles. It also plays an important role in industrial automation. Control engineers often utilize feedback when designing control systems. For example, in an automobile with cruise control the vehicle's speed is continuously monitored and fed back to the system which adjusts the motor's power output accordingly. Where there is regular feedback, control theory can be used to determine how the system responds to such feedback. Electrical engineers also work in robotics to design autonomous systems using control algorithms which interpret sensory feedback to control actuators that move robots such as autonomous vehicles, autonomous drones and others used in a variety of industries. Electronic engineering involves the design and testing of electronic circuits that use the properties of components such as resistors, capacitors, inductors, diodes, and transistors to achieve a particular functionality. The tuned circuit, which allows the user of a radio to filter out all but a single station, is just one example of such a circuit. Another example to research is a pneumatic signal conditioner. Prior to the Second World War, the subject was commonly known as radio engineering and basically was restricted to aspects of communications and radar, commercial radio, and early television. Later, in post-war years, as consumer devices began to be developed, the field grew to include modern television, audio systems, computers, and microprocessors. In the mid-to-late 1950s, the term radio engineering gradually gave way to the name electronic engineering. Before the invention of the integrated circuit in 1959, electronic circuits were constructed from discrete components that could be manipulated by humans. These discrete circuits consumed much space and power and were limited in speed, although they are still common in some applications. By contrast, integrated circuits packed a large number—often millions—of tiny electrical components, mainly transistors, into a small chip around the size of a coin. This allowed for the powerful computers and other electronic devices we see today. Microelectronics engineering deals with the design and microfabrication of very small electronic circuit components for use in an integrated circuit or sometimes for use on their own as a general electronic component. The most common microelectronic components are semiconductor transistors, although all main electronic components (resistors, capacitors etc.) can be created at a microscopic level. Nanoelectronics is the further scaling of devices down to nanometer levels. Modern devices are already in the nanometer regime, with below 100 nm processing having been standard since around 2002.Microelectronic components are created by chemically fabricating wafers of semiconductors such as silicon (at higher frequencies, compound semiconductors like gallium arsenide and indium phosphide) to obtain the desired transport of electronic charge and control of current. The field of microelectronics involves a significant amount of chemistry and material science and requires the electronic engineer working in the field to have a very good working knowledge of the effects of quantum mechanics. Signal processing deals with the analysis and manipulation of signals. Signals can be either analog, in which case the signal varies continuously according to the information, or digital, in which case the signal varies according to a series of discrete values representing the information. For analog signals, signal processing may involve the amplification and filtering of audio signals for audio equipment or the modulation and demodulation of signals for telecommunications. For digital signals, signal processing may involve the compression, error detection and error correction of digitally sampled signals.Signal Processing is a very mathematically oriented and intensive area forming the core of digital signal processing and it is rapidly expanding with new applications in every field of electrical engineering such as communications, control, radar, audio engineering, broadcast engineering, power electronics, and biomedical engineering as many already existing analog systems are replaced with their digital counterparts. Analog signal processing is still important in the design of many control systems. DSP processor ICs are found in many types of modern electronic devices, such as digital television sets, radios, Hi-Fi audio equipment, mobile phones, multimedia players, camcorders and digital cameras, automobile control systems, noise cancelling headphones, digital spectrum analyzers, missile guidance systems, radar systems, and telematics systems. In such products, DSP may be responsible for noise reduction, speech recognition or synthesis, encoding or decoding digital media, wirelessly transmitting or receiving data, triangulating position using GPS, and other kinds of image processing, video processing, audio processing, and speech processing. Telecommunications engineering focuses on the transmission of information across a communication channel such as a coax cable, optical fiber or free space. Transmissions across free space require information to be encoded in a carrier signal to shift the information to a carrier frequency suitable for transmission; this is known as modulation. Popular analog modulation techniques include amplitude modulation and frequency modulation. The choice of modulation affects the cost and performance of a system and these two factors must be balanced carefully by the engineer. Once the transmission characteristics of a system are determined, telecommunication engineers design the transmitters and receivers needed for such systems. These two are sometimes combined to form a two-way communication device known as a transceiver. A key consideration in the design of transmitters is their power consumption as this is closely related to their signal strength. Typically, if the power of the transmitted signal is insufficient once the signal arrives at the receiver's antenna(s), the information contained in the signal will be corrupted by noise. Instrumentation engineering deals with the design of devices to measure physical quantities such as pressure, flow, and temperature. The design of such instruments requires a good understanding of physics that often extends beyond electromagnetic theory. For example, flight instruments measure variables such as wind speed and altitude to enable pilots the control of aircraft analytically. Similarly, thermocouples use the Peltier-Seebeck effect to measure the temperature difference between two points

A voltage source (V) is modeled by connecting its internal impedance (Zg) in series. If we determine the impedance across the voltage source terminals, it should be Zg, and it is possible only if the voltage source is short-circuited.

An equivalent current source is modeled by connecting the current source (V/Zg) in parallel with the internal impedance Zg. For the two sources to be equivalent, their impedances across their terminals must be equal. This is possible only if the current source is open-circuited.

There are several type of circuit breakers now a day we are using these are as follows:

1. M.C.B. (Miniature circuit Breaker)

Rating : 1, 2, 4, 6, 10, 16, 20, 25, 32, 63 Amperes

2. M.C.C.B. (Miniature current circuit Breaker)

Rating : 10, 16, 20, 25, 32, 63, 100, 200, 250, 400 Amperes.

3. A.C.B. (Air Circuit Breaker)

Rating : 400, 800, 1000, 1200, 1500, 1800, 2000 Amperes.

4. A. B. Switch (Air Breaker)

used in High tension line.

5. SF6 Breaker (Contact break in the Sf6 medium)

used in High tension line.

Yes, a three phase motor can run on a DC supply. You will need to provide an inverter, or a motor-generator set to do so. (In practical terms, the answer is no, because the costs will be high for any kind of significant power.)

It is simple. Resistance is the measure of how strongly a material resists a current.

Power transformers have an impedance (Z) rating that is listed in %. So the nameplate might state 5% Z for example. What this means is that when the secondary conductors are bolted together then 5% of the rated primary voltage is applied and will generate 100% current in flow in the secondary.

Example: you have a 75KVA Delta-Wye 5% Z transformer with a 480V primary rating and 208/12 secondary rating. The amp rating of the secondary is 208A [75,000/(1.732x208)]

So if you applied 24VAC to the primary with the secondary bolted together with busbar then you would have 208A of current flow.

The fuses are held by spring metal clips , the clips are themselves being permanently connected to the circuit conductors.

In general, it is cheaper to transport power long distances at higher voltage levels. Do not take this as a rule as always being cheaper, otherwise you would have a 500kV line into your home.

The resistance in the power company's lines is not zero. There is always going to be some loss in quality whenever energy is transferred. Thus, when electricity is transferred, the power dissipated by the lines, even lines with a REALLY small resistance, like 1 micro-ohm per mile, adds up when one counts the millions of linear miles across which electricity is transmitted. The power dissipated can be calculated with the formula, P= VI, which through Ohm's law becomes P = (I^2) x R, where P = Power dissipated, V = voltage, I= current, and R= resistance. Thus, using the same resistance wire and the same power source, a higher voltage will have a lower current and less power will be dissipated as heat.

It is not cheaper to transport electric power at high voltages. What we are looking for is the smallest amount of loss during that transfer. The higher the voltage the lower the percentage of loss for a given diameter of wire. The costs associated with stations to step up and down power and to maintain these stations is very high. What the goal is here though is making as much power as possible reach our final destination. This is also why we use aluminum wire for transfer rather then copper. It is all about reduced loss, cost is a secondary concern.

refer the article http://www.msha.gov/S&HINFO/TECHRPT/GROUND/SAFEMEAS.pdf

In a voltage follower, voltage gain is 1, with an offset of VB-E, and current gain is hFe, limited, of course, by the available current in the supply and by the rating of the transistor.

RMS stands for Root Mean Square. Basically it's what your AC voltmeter measures. So if you have a 120 volt AC signal, what you are saying is that the measured RMS voltage of the signal is 120 volts.
The RMS voltage is a measure of the equivalent heat of a DC voltage. So a 120 volts RMS AC signal, which varies between +168 volts and -168 volts and back 60 times every second, has the same heating power that a DC voltage of 120 VDC would have.

RMS voltage divided by 0.707 equals peak to peak voltage.

Alternative Answer
Think of two types of electric saw: a circular saw and a reciprocating saw. We measure the speed of these two saws in two different ways, revolutions per second and strokes per second. Is there any way of comparing the two? Well, yes, we could describe both in terms of the length of cut they would make in the same period of time (their cutting speeds).

Following this analogy, we compare direct current and alternating current by determining the heating effect of both currents. For example, if a direct current of, say, 10 A, produces a heating effect of x joules, what value of alternating current would produce exactly the same heating effect? Well, an experiment would show that this would be 0.707 times the amplitude (peak value) of that AC current which, in this particular example, would be a little over 14 A. So, instead of specifying the current's peak value, we always specify its rms-value.

Since voltage and current are proportional to each other, we can measure voltage in the same way -i.e. Vrms = 0.707 Vmax. So, as the first answer explains, a nominal voltage of 120 V actually peaks at 168 V.

(You may ask, why not simply use an average, rather than rms value? Well, apart from the fact you wouldn't be able to compare it to DC, the average of a complete positive/negative cycle would be zero!)