Electrical Engineering

What are different types of Control Systems? Two major types of Control Systems are 1) Open loop Control System 2) Closed Loop Control Systems Open loop Control Systems: The Open loop Control System is one in which the Output Quantity has no effect on the Input Quantity. No feedback is present from the output quantity to the input quantity for correction. Closed Loop Control System: The Closed loop Control System is one in which the feedback is provided from the Output quantity to the input quantity for the correction so as to maintain the desired output of the system.

What is Control System? In a System the output and inputs are interrelated in such a manner that the output quantity or variable is controlled by input quantity, then such a system is called Control System. The output quantity is called controlled variable or response and the input quantity is called command signal or excitation.

super-conductivity : The electrical resistance of a metal or alloy which decreases with decrease in temperature and becoming vanishingly small at a finite temperature.

SRAM : Static RAM. A RAM that stores information in flip flop cells which do not have to be refreshed unlike those of the DRAM.

Solenoid : A coil of wire wound uniformly on a cylindrical former, having a length which is large compared with its radius.

Band gap : In a semiconductor, the energy difference between the highest valence band and the lowest conduction band.

Valence band : The highest energy band in a semiconductor that can be filled with electrons.

Conduction band; Conduction level : Energy level at which electrons are not bound to (orbiting) a specific atomic nucleus but are free to wander among the atoms. An energy band in which electrons can move freely in a solid, producing a net transport of charge.

Superconductivity : The pairing of electrons in certain materials when cooled below a critical temperature, causing the material to lose all resistance to electricity flow. Superconductors can carry electric current without any energy losses.

Drift Velocity? If a particle moves in space in such a manner that it randomly changes its directions and velocities, the resultant of these random motions as a whole is called drift velocity. The definition of drift velocity can be understood by imagining the random motion of free electrons in a conductor. The free electrons move in a conductor with random velocities and random directions. When we apply an electric field across the conductor, the randomly moving electrons experience an electrical force in the direction of the field. Due to this field, the electrons do not give up their randomness of motion, but they will shift towards higher potential with their random motion. That means the electrons will drift towards higher potential along with their random motions. Thus, every electron will have a net velocity towards the higher potential end of the conductor, and we refer this net velocity as the drift velocity of electrons. Hopping, you understand the definition of drift velocity. The current due to this drift movement of electrons inside an electrically stressed conductor, is known as drift current. It is needless to say that every electric current is "drift current".

What are Energy Bands? A large number of atoms in a crystal stone is closer to each other and more those electrons interact with themselves. The energy level of electrons in their shell is only caused because of the modification in their energy levels. The most important feature of Energy Bands is that the energy states for electrons are continuous in varied ranges. Thus, we can say that the energy level of an atom vary in valence bands and in conduction bands. Since the electrons interact with other electrons, the energy associated with a material is altered so, the electrons are associated with a band of energy levels. The collection of energy levels which are partially or wholly filled are called valence band, and they are never empty. The collection of energy levels of the free electron which move freely around the material are called conduction band. There is an extra energy required to the conduction band by the valence electrons to move, which is termed as Forbidden energy. Depending on the material the energy band theory is classified as:  Conductors  Insulators  Semiconductors

Capacitance: (or C, measured in farads), dictates the amount of charge that can be stored at a given voltage (a one-farad capacitor charged to one volt will hold one Coulomb of charge).

Reactance: That part of the impedance that does not consume active power. It is the imaginary part of the impedance.

Admittance: Reciprocal of impedance. Ratio of the electric current to the voltage. [Unit: siemens or S]

Impedance: Impedance, represented by the symbol Z, is a measure of the opposition to electrical flow. It is measured in ohms. For DC systems, impedance and resistance are the same, defined as the voltage across an element divided by the current (R = V/I).

Ans. is "Voltage."

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The Circuit Breakers according to the voltage levels they can operate on : 1.Low Voltage Circuit Breakers (< 1 kV) 2.Medium Voltage Circuit Breakers (1-72 kV) 3.High Voltage Circuit Breakers (> 72 kV) Very important category is where to use the circuit breakers: 1.Outdoor circuit breaker 2.Indoor circuit breaker There is another category which is based on the mechanism used to actuate the circuit breaker, which specifies the mechanism of operation of the breaker, there are three further types: 1.Spring operated circuit breaker 2.Pneumatic circuit breaker 3.Hydraulic circuit breaker Now considering the medium in which a circuit breaker can operate: 1.Oil circuit breaker. 2.Air Blast circuit breaker. 3.SF6 circuit breaker. 4.Vacuum circuit breaker.

What is Circuit breaker? Circuit breaker is a switching device which can be operated manually as well as automatically for controlling and protection of electrical power system respectively.