Electrical engineering is an engineering discipline that deals with the study and application of electricity and electromagnetism. Its practitioners are called electrical engineers. Electrical engineering is a broad field that encompasses many subfields.
Electrical engineering has many subfields dealing with the various aspects of electromagnetism. Some work directly with Maxwell's equations to manipulate RF signals, some with power, and some with signal manipulation.
In the subfield of electronics, electrical engineers design and test electrical networks (more commonly known as circuits) that take advantage of electromagnetic properties of electrical components or discretes/elements (such as resistors, capacitors, inductors, transistors, diodes, semiconductors) to achieve the desired functionality. One of several ubiquitous examples is the tuner circuit, which allows the user of a radio to filter out all but a single station, corresponding to a desired signal frequency (see AM radio or FM radio).
Electronics really began when Lee de Forest invented the Audion in 1907 (a triode vacuum tube), adding a grid electrode to the Fleming valve, inspired by Edison's electric lamp. Within 10 years, the Audion was in use for radio transmitters and receivers as well as allowing coast to coast telephone calls. Vacuum tubes remained the preferred amplifying device for 40 years, until researchers working for William Schockley at Bell Labs invented the transistor in 1947. In the following years, transistors made a small portable radio possible (Transistor radio), as well as allowing more powerful mainframe computers to be built, since transistors were cooler and required lower voltages than vacuum tubes.
Before the invention of the integrated circuit, electronic circuits were constructed from discrete components that could be manipulated by hand. These non-integrated circuits consume much space and electrical power, are prone to failure, and are limited in speed, though they are still common in simple applications. The integrated circuit, by contrast, packs large numbers--often millions--of tiny electrical components, mainly transistors, onto a small chip which is typically the size of a coin. The thought of hand-assembling millions of elements into a small, reliable assembly should be enough to convince one that the integrated circuit is responsible for the technological revolution experienced in the latter half of the twentieth century.
In designing an integrated circuit, electrical engineers first construct circuit schematics (drawings) that specify electrical components and describe interconnections among the electrical components. When the schematics are completed, VLSI engineers convert the schematics into actual layouts, which literally map out layers of various conductor and semiconductor materials (such as metal and polysilicon) on a scale of micrometres and nanometres. The conversion from schematics to layouts can be done by computer programs, although very often human fine-tuning is desirable to decrease space and power consumption.
The physical fabrication of integrated circuits is itself a huge subfield of electrical engineering, on which circuit designers must rely. As transistors become tinier--approaching atomic dimensions--microelectronic circuit designers must involve themselves more and more in the fabrication process (see photolithography). Electrical engineers and mechanical engineers have essentially joined together in the creation of Micro Electro-Mechanical Systems (MEMS), which designs micrometre-sized machines within integrated circuits (e.g., accelerometers).
Software simulation is essential in the design process of electronic circuits, especially integrated circuits (see SPICE or Cadence Design Systems). Models of semiconductor materials and electrical components are constructed by fabrication plants (fabs) and manufacturers of electrical components for the purpose of simulation.
Integrated circuits and discretes are then combined into printed circuit boards (PCBs). PCBs commonly have a distinctive green color and can usually be found in any electronic device (e.g., televisions, computers, digital audio players).
An electrical power tower
Power engineering tends to deal with electricity generation, transmission and distribution. These three areas make up a power grid that is used to provide industry, commerce and residents electrical power. Both direct current (DC) and alternating current (AC) can be used to transmit power from the generator to the user. However, three-phase AC is more heavily used over High-voltage direct current (HVDC).
Power engineering is also concerned with electrical circuits and materials (e.g. insulators, semiconductors) that need to withstand the high voltages and currents that transmissions use. Voltages used are much higher than found in homes, which can vary from a few thousand volts to several hundred thousand voltage and can move hundreds of megawatts.
Today, only a few universities have programs or do research in power engineering (e.g., Iowa State University).
Digital signal processing
Digital signal processing (DSP) is a field mixed with computer engineering to process and manipulate signals. The signals can be any electrical signal from audio (see Audio signal processing) to voltages to images (see Digital image processing). Utilizing the flexibility of digital computers, DSP is typically performed in software but could easily be performed in hardware through the use of field-programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs) or other programmable hardware devices.
One important concern in DSP is sampling where analog-to-digital conversion and digital-to-analog conversion are used to interface the "digital world" with the real world.
DSP has become a very important field for instrumentation and telecommunications that often use statistical properties of the signal to enhance the signal. Location finding of cellular phone users has become an issue when dialing an emergency telephone number such as 9-1-1 in the US/Canada. With cellular phones, by their nature of being mobile, the user could be in an unfamiliar area and thus unable to give a location.
Another subfield is accurate measurement of electrical properties. For example, the oscilloscope is used to measure voltage. Measuring an electrical circuit inevitably changes the voltages and currents in it. The objective is to minimize the influence of the measuring circuit or even compensate for it. The field also includes sensors that use a material's electrical properties, or electromechanical means of measurement. Examples of the former are piezoelectricity for measuring pressure and temperature-dependent resistors for measuring temperature.
These sensors can be used in control engineering to sense the environment and make control decisions through electric motors and actuators.
Other major subfields of electrical engineering are telecommunication and electromagnetism. Transmitting information from one place to another requires a transport channel such as a coax cable, optical fiber or free space. These channels can be accurately described using the laws of electromagnetism, particularly Maxwell's equations.
Some other examples of how electromagnetism is put to every day use are antenna design for use in mobile phones, and controlling the form of the electromagnetic field in an MRI scanner by the exact placement and alignment of its electromagnets. Another technology made possible by electromagnetism is the microwave oven.
The field of high-power radio frequency engineering (RF engineering) was once feared to be a lost art. Because of the trend for low-power, miniaturized circuitry, there is a perception that the need for high-power radio engineering and engineers is diminishing. On the contrary, the need for engineers and technicians in this particular field has never been greater, and the need will only increase in the foreseeable future.
Broadcast engineering combines several aspects of electrical engineering, including telecommunications, radio frequency, audio, video (television), and computers. Audio engineering combines electrical engineering with the physics of acoustics.
Theories and tools
The theories and tools an electrical engineer can consult include mathematics and physics in general, the theory of electromagnetism, the theory of quantum mechanics, the mathematics of classical signal and system theory, statistical communication theory, digital signal processing, Information Theory, control theory, and the teachings of computer science. See also the concepts of automaton and finite state machine (FSM).
Biotechnology such as EEG,ECG (EKG), various other monitoring equipment as well as automated intravenous drug/serum flow control, life support systems, etc.
Electronics: integrated circuit, computer, electronic amplifier
Power engineering: electrical generators, electric power transmission
Telecommunication: television, radio, mobile phone
Electromagnetism: radar, stealth aircraft
Control engineering: auto pilot, cruise control, climate control, space exploration, smart bomb
Signal processing: electronic filter, digital filter, video and audio codec, radar, sonar, beamforming
Of course, everything is really a product of multiple subfields.
The Institute of Electrical and Electronics Engineers (IEEE) and the Institution of Electrical Engineers (IEE) are prominent non-profit organizations for electrical engineers that publish standards, publications and periodicals and organise conferences and workshops. The IEEE is the largest professional organization in the world.
Progressive miniaturisation in the production of electrical networks using semiconductor device fabrication has led to the development of complete systems on a single chip, a process called very-large-scale integration (VLSI). Microprocessors are a result of this evolution. This subfield spawned the related discipline of computer engineering.
Electronics that deal with both electrons (electricity) and light are also called optoelectronics. The related field of fibre optics has led to the development of fast telecommunication systems and the expansion of the Internet.
On the boundary of mechanical engineering and electrical engineering, mechatronics push the boundaries of what mechanical components can do and their integration with electronics. For example, the precise positioning of the laser in a compact disc player to follow a track is only possible due to electronics designed to compensate for the vibrations, the loss of focus, the irregularities in the disc, etc.