Electrical World

When charges are separated, a space is created where forces are exerted on the charges. An electric field is such a space. Depending upon the polarity of the charges, the force is either attractive or repulsive. Therefore, we can say that static charges generate an electric field. An electric field influences the space surrounding it. Electric field strength is determined in terms of the force exerted on charges. A capacitor is a reservoir of charge. The two parallel plates of a capacitor, when connected to a voltage source, establishes an electric field between the plates. The positive terminal, or pole of the voltage source will draw electrons from plate 1 whereas the negative pole will push extra electrons on to plate 2. Voltage across the capacitor will rise. The capacitor gets charged equal to the voltage of the source. The capacitance of a capacitor is a measure of its ability to store charge. The capacitance of a capacitor is increased by the presence of a dielec...

Several theories have been developed to explain the nature of electricity. The modern electron theory of matter, propounded by scientists Sir Earnest Rutherford and Niel Bohr considers every matter as electrical in nature. According to this atomic theory, every element is made up of atoms which are neutral in nature. The atom contains particles of electricity called electrons and protons. The number of electrons in an atom is equal to the number of protons. The nucleus of an atom contains protons and neutrons. The neutrons carry no charge. The protons carry positive charge. The electrons revolve round the nucleus in elliptical orbits like the planets around the sun. The electrons carry negative charge. Since there are equal number of protons and electrons in an atom, an atom is basically neutral in nature. If from a body consisting of neutral atoms, some electrons are removed, there will be a deficit of electrons in the body, and the body will attain positive charge...

 Last time, we studied the first part of Learn Electrical Engineering for Beginners and this is all about DC Circuits. Today, we will be dealing with our Part 2 of our module and this is all about Alternating Current Circuits.   So, you may now start to learn what this ac is and how it behaves. Alternating Current does not flow through a conductor in the same direction as what dc does. Instead, it flows back and forth in the conductor at the regular interval, continually reversing its direction of flow and can do so very quickly. It is measured in amperes, just as dc is measured too. Remember, one couloumb of electrons is passing a given point in a conductor in one second. This definition also applies when ac is flowing- only now some of the electrons during that 1 second flow past the given point going in one direction, and the rest flow past it going in the opposite directions. Difference between DC and AC The industrial applications of alternating c...

A voltage can be developed in a coil of wire in one of the three ways: 1. By changing the flux through the coil. 2. By moving the coil through the magnetic field. 3. By altering the direction of the flux with respect to the coil. The first one is that voltage is said to be induced emf and in accordance with Faraday's law, its magnitude at any instant of time is given by the formula as shown below: e = N(dΦ/dt) x 10 -8 volts where N is the number turns in a coil dΦ/dt = rate at which the flux in maxwells changes through the coil Please take note that in this method of developing an emf, there is no physical motion of coil or magnet; the current through the exciting coil that is responsible for the magnetism is altered to change the flux through the coil in which the voltage is induced. For the second and third method mentioned above, there is actual physical motion of coil or magnet, and in altered positions of coil or magnet flux through the coil chang...

There are two facts that the voltage developed in a coil of a generator changes; the first one is it changes in magnitude from instant to instant as varying values of flux are cut per second and the other one is it changes in direction as coil side change positions under north and south poles , implies that alternating emf is generated. This means that the voltage is maximum as mentioned in our last topic here when the position of the coil is just like shown in the figure below: Initial position of the coil and will diminish to zero as the coil rotates clockwise toward the position as shown below: As the coil rotates clockwise Then, as the coil continues to rotate clockwise, the polarities will change. Assuming uniform flux distribution between north and south poles, the generated voltage in a coil located from the vertical will be: e = Em sin α Consider the figure below for us to analyze why this relationship mentioned above happened. Illustrating the ...

INTRODUCTION Electrical engineering is a field of engineering that generally deals with the study and application of electricity , electronics and electromagnetism . The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical power supply. It now covers a range of subtopics including power , electronics , control systems , signal processing and telecommunications . Electrical engineering may or may not include electronic engineering . Where a distinction is made, usually outside of the United States, electrical engineering is considered to deal with the problems associated with large-scale electrical systems such as power transmission and motor control , whereas electronic engineering deals with the study of small-scale electronic systems including computers and integrated circuits . Alternatively, electrical engineers are usually concerned with using electricity to transmit energy, ...

Ques.[1] For torque transmission over a long distance with the help of electrical wires only, which of the following two synchros are used ? (a)CX and CT (b)CX and CR (c)CX and CD (d)CT and CD Answer :B  Ques.[2] Squirrel-cage induction motor is finding increasing application in high-power servo systems because new methods have been found to (a) increase its rotor resistance (b) control its torque (c) decrease its intertia (d) decouple its torque and flux.   Answer:D   Ques.[3] The control ........................ synchro has three- phase winding both on its stator and rotor. (a) differential (b) transformer (c) receiver (d) transmitter Answer:A  Ques.[4] A dc servomotor is similar to a regular d.c. motor except that its design is modified to cope with (a) electronic switching (b) slow speeds (c) static conditions (d) both (b) and (c).   Answer:D  Ques.[4] The low-torque synchros cannot be used for (a) torque transmiss...

Q: Do you know the advantages of speed controlusing thyristor? A: Advantages: 1. Fast Switching Characterstics than Mosfet, BJT, IGBT 2. Low cost 3. Higher Accurate. Q: Name the different types of motors used in vacuum cleaners, phonographic appliances, vending machines, refrigerators, rolling mills, lathes, power factor improvement and cranes. A: Following motors are used: - • Vacuum cleaners- Universal motor. • Phonographic appliances – Hysteresis motor. • Vending machines – Shaded pole motor. • Refrigerators – Capacitor split phase motors. • Rolling mills – Cumulative motors. • Lathes – DC shunt motors. • Power factor improvement – Synchronous motors. Q: In the motors starting purpose why the armature rheostats at maximum position while the field rheostat is kept in minimum position? A: In the time of starting a motor the field rheostat is kept in minimum state for the high starting torque. In the time of starting a motor the armature rheostats is used to control or reduce the h...

Q :Why link is provided in neutral of an ac circuit and fuse in phase of ac circuit? A :Link is provided at a Neutral common point in the circuit from which various connection are taken for the individual control circuit and so it is given in a link form to withstand high Amps. But in the case of Fuse in the Phase of AC circuit it is designed such that the fuse rating is calculated for the particular circuit (i.e load) only.So if any malfunction happen the fuse connected in the particular control circuit alone will blow off. Q :State the difference between generator and alternator A :Generator and alternator are two devices, which converts mechanical energy into electrical energy. Both have the same principle of electromagnetic induction, the only difference is that their construction. Generator persists stationary magnetic field and rotating conductor which rolls on the armature with slip rings and brushes riding against each other, hence it converts the induced em...

Q : How can you start-up the 40w tube lite with 230v AC/DC without using any choke/Coil? A : It's possible with Electronic choke. otherwise it's not possible to ionize the particles in tube. light, with normal voltage. Q :What types domain of Laplace transforms? What behavior can Laplace transform predict how the system work? A :Types domain of Laplace transforms is s-domain, Laplace transforms provide a method to find position, acceleration or voltage the system will have. Q :In the magnetic fluxes, what is the role of armature reaction? A : The armature flux has an important role for the running condition. This armature flux can oppose the main flux or it may support the main flux for better running condition. This effect of supporting and opposing of main flux to armature flux is called armature reaction. Q :Explain thin film resistors and wire-wound resistors A :a:Thin film resistors- It is constructed as a thin film of resistive material is deposited on ...

Q :How to determine alternating current frequency? A :Zero crossings of the sine wave to trigger a monostable (pulse generator) is a way to determine alternating current frequency. A fixed width pulse is generated for each cycle. Thus there are "n" pulses per second, each with with a constant energy. The more pulses there are per second, the more the energy. The pulses are integrated (filtered or averaged) to get a steady DC voltage which is proportional to frequency. This voltage can then be displayed on an analogue or digital voltmeter, indicating frequency. This method is more suitable than a direct counter, as it can get good accuracy in a second or so .   Q :Why electricity in India is in the multiples of 11 like 11kv, 22kv, 33kv  ? A :Transformer Induced voltage equation contains 4.44 factor.  E=4.44*f*T*phi  E -Induced emf per phase  T -number of turns  f -frequency  phi -maximum flux per pole  From the eq...

Q uery : Difference between megger test equipment and contact resistance meter test instruments? Resolution : Megger test equipment used to measure cable electric resistance, conductor continuity, phase identification where as contact resistance meter test instruments used to measure low resistance like relays ,contactors. Q uery :When we connect the large capacitor bank in series ? Resolution :we connect large capacitor bank in series to improve the voltage power supply at the load end in balanced transmission line when there is considerable voltage drop along the balanced transmission line due to high impedance of the line.So in order to bring the voltage at the load terminals within its limits (i.e (+ or - %6 )of the rated high terminal voltage )the large capacitor bank is used in series. Q uery : What is electrical diversity factor in electrical installations? Resolution :Electrical diversity factor is the ratio of the sum of the individual maximum dem...

Query :What is the function of interposing current transformer?   Resolution :The main function of an interposing current transformer is to balance the currents supplied to the relay where there would otherwise be an imbalance due to the ratios of the main current transformers.  Interposing current transformer are equipped with a wide range of taps that can be selected by the user to achieve the balance required.  Query :What are Motor Generator Sets and explain the different ways the motor generator set can be used ?   Resolution :Motor Generator Sets are a combination of an electrical generator and an engine mounted together to form a single piece of equipment. Motor generator set is also referred to as a genset, or more commonly, a generatorThe motor generator set can used in the following different ways:                1.Alternating current (AC) to direct current (DC) ...

Q:How do you select a cable size (Cu & Al) for a particular load? A :At first calculate the electrical current of the load, after that derate the electrical current considering derating factor(depending on site condition and laying of cable) after choose the cable size from cable catalog considering derating electrical current.After that measure the length of cable required from supply point of load to load poin. Calculate the voltage drop which will max 3% (resistance and reactance of cable found from cable catalog of selecting cable) if voltage drop>3% then choose next higher size of cable. Q:What are HRC fuses and where it is used? A :HRC stand for "high rupturing capacity" fuse and it is used in distribution system for electrical transformers. Q:Which power plant has high load factor? A :All base load power plants have a high load factor. If we use high efficiency power plants to supply the base load,we can reduce the cost of generation.Hydel p...