Basic engineering questions and answers download

It can be measured by allowing the flow of water from a hydrant and noting down the horizontal distance x where jet strikes the ground and the vertical distance y of outlet from ground. For the same size, length and condition of pipe, how the friction head loss changes if pipe size is varied.

Under same flow conditions the friction head loss increases as the size change to the 4. How does the capacity changes in pipe flow with increase in pipe diameter if head is constant? At constant head, capacity is proportional to d How does the head change in pipe flow with change in diameter, if capacity is constant.

At constant capacity, head is proportional to. How head varies in pipe flow with change in flow, if pipe diameter is same. At constant diameter, head is proportional to flow 2. Define the term contraction coefficient. The ratio of area of jet contracted and the cross section of the orifice. What for pycnometer is used? Pycnometer is used to measure specific gravity of the liquid. Name various functional elements of an instrumental system?

Name the three stages of a generalised measuring system. How is a Pelton turbine braked? A pelton wheel is braked by a nozzle directing a jet on the back of the buckets. What is static pressure? How is it measured.

The pressure caused on the walls of a pipe due to a fluid at rest inside the pipe or due to the flow of a fluid parallel to walls of the pipe is called static pressure. This static pressure is measured by inserting a pressure measuring tube into the pipe carrying the fluid so that the tube is at right angle to the fluid flow path.

What are the requirements of a control system? Stability, accuracy and speed of response are the three requirements of control system. What is the difference between weir, and submerged weir.

Any obstruction of a streamflow over which water flows is weir. When the downstream water level rises over the weir crest, it is called submerged weir.

What is the difference between spillway and siphon spillway? Spillway is an essential part of a large dam and provides an efficient and safe means of releasing flood water that exceeds the design capacity of the reservoir. Siphon spillway is spillway designed to discharge water in a closed conduit under negative pressure.

What is the difference between culverts, stilling basin, and standpipe? Culverts are built at the points of lowest valley to pass water across the embankments of highways or railroads. Stilling basin is transitional energy dissipating structure to avoid the damaging process by a highly accelerated spilled water. Standpipe is used principally for alleviating the transient pressures in large pipeline system.

It also works as a pressure relief valve for the upstream pipe during the turbine shut off. What do you understand by run-of-river scheme in hydro power generation? A scheme in which the discharge is varying and only that much water can be utilised for conversion as available in the river. What is the difference between firm power and secondary power in hydro power plants?

The approximate constant and continuous power which is assured at power station and would be available throughout the year is called firm power. What is the criterion for determining economic diameter of power tunnel? The economic diameter of a power tunnel is determined such that the total value of following two factors is least i annual loss of revenue on account of power head lost due to friction.

What are the three functions served by a surge tank in a hydro plant? The three functions served by a surge tank are i flow regulation — act as a reservoir for acceptance or delivery of water to meet requirements of load changes. What is the criterion to determine the economic diameter of penstock? The economic diameter of a penstock required to carry a discharge is the one at which annual costs due to the greater investment do not exceed the annual value of resulting increment energy output.

If jet ratio for a pelton wheel is 12 then number of buckets should be …. What is the difference between anti-friction and hydrostatic bearings?

In anti-friction bearings rolling components are introduced between the sliding surfaces. In hydrostatic bearings lubricant is supplied at a high pressure to a pocket in the bearing. State law of conservation of momentum? The ratio of change of momentum of a mass of fluid is equal to the vector sum of all external forces acting on it. Define turbulent flow? Flow in which adjacent layers mix continuously, so that the flow pattern is unsteady, full of eddies, and apparently without any mathematically expressible regularity.

What is the difference between boundary lubrication and fluid film lubrication? I worked in plant so i need. Your email address will not be published. Electronic Meters Digital Electronics :- Logic Circuits Integrated Circuits :- Posted on by 18 Comments.

Sir plz send me PDF to prepare for electrical and electronics core competencies. Please sir send me ongc exam preparation related questions PDF file. What is frantic effect? Output voltage is greater than the input voltage or receiving end voltage is greater than the sending end voltage.

What is meant by insulation voltage in cables? It is the property of a cable by virtue of it can withstand the applied voltage without rupturing it is known as insulation level of the cable. The two types of earthing are Familiar as Equipment earthing and system earthing. In Equipment earthing: body non conducting part of the equipment shouldd be earthed to safegaurd the human beings. With this,in case of unbalanced loading neutral will not be shifted.

We can protect the equipment also. With size of the equipment transformer or alternator and selection of relying system earthing will be further classified into directly earthed,Impedance earthing, resistive NGRs earthing. MCB is miniature circuit breaker which is thermal operated and use for short circuit protection in small current rating circuit. MCCB moulded case circuit breaker and is thermal operated for over load current and magnetic operation for instant trip in short circuit condition.

Normally it is used where normal current is more than A. Where should the lighting arrestor be placed in distribution lines? Near distribution transformers and out going feeders of 11kv and incomming feeder of 33kv and near power transformers in sub-stations.

Define IDMT relay? It is an inverse definite minimum time relay. In IDMT relay its operating is inversely proportional and also a characteristic of minimum time after which this relay operates. It is inverse in the sense ,the tripping time will decrease as the magnitude of fault current increase. What are the transformer losses? Copper losses are caused by the resistance of the wire I2R. Magnetic losses are caused by eddy currents and hysteresis in the core.

Copper loss is a constant after the coil has been wound and therefore a measurable loss. Hysteresis loss is constant for a particular voltage and current. Eddy-current loss, however, is different for each frequency passed through the transformer. What is the count of hvdc transmission lines in India? Resolution:At present there are three hvdc transmission lines in india. What is meant by regenerative braking? Resolution:When the supply is cutt off for a running motor, it still continue running due to inertia.

In order to stop it quickly we place a load resitor across the armature winding and the motor should have maintained continuous field supply. Why is the starting current high in a DC motor? At starting, Eb is zero. What are the advantages of star-delta starter with induction motor? Resolution: 1. The main advantage of using the star delta starter is reduction of current during the starting of the motor. Starting current is reduced to times Of current of Direct online starting.

Hence the starting current is reduced , the voltage drops during the starting of motor in systems are reduced. Resolution:For lighting loads, neutral conductor is must and hence the secondary must be star winding. To minimize the current unbalance in the primary we use delta winding in the primary.

Why in a three pin plug the earth pin is thicker and longer than the other pins? It is longer because the The First to make the connection and Last to disconnnect should be earth Pin. This assures Safety for the person who uses the electrical instrument. Why series motor cannot be started on no-load? Resolution:Series motor cannot be started without load because of high starting torque. Series motor are used in Trains, Crane etc. Resolution:ELCB is used to detect earth leakage fault.

Once the phase and neutral are connected in an ELCB, the current will flow through phase and that much current will have to return neutral so resultant current is zero. Once there is a ground fault in the load side, current from phase will directly pass through earth and it will not return through neutral through ELCB.

That means once side current is going and not returning and hence because of this difference in current ELCB wil trip and it will safe guard the other circuits from faulty loads.

If the neutral is not grounded, fault current will definitely high and that full fault current will come back through ELCB, and there will be no difference in current. How electrical power is generated by an A. C Generator? For the generation of elect power we need a prime mover which supplies mechanical power input to the alternator, can be steam turbines,or hydro turbines. When poles of the rotor moves under the armature conductors which are placed on the stator ,field flux cut the armature conductor ,therefore voltage is generated and is of sinusoidal in nature…due to polarity change of rotor poles i,e N-S-N-S.

Why an ac solenoid valve attract the plunger even though we interchanges the terminal? Will the poles changes? Yes because the poles changes for every half-cycle of ac voltage so the polarity of AC voltage is continuously changing for every half cycle. What is derating? The current currying of cables will change depending upon the site temperature location of site , type of run it will run through duct, trench, buried etc.

Considering this condition actual current currying capacity of cable reduce than current currying capacity which given to cable Catalogue this is called derating.

Why temperature rise is conducted in bus bars and isolators? Bus bars and isolators are rated for continuous power flow, that means they carry heavy currents which rises their temperature. When voltage increases then current also increases then what is the need of over voltage relay and over current relay? Can we measure over voltage and over current by measuring current only? So, for a better protection of the system. If one lamp connects between two phases it will glow or not?

If the voltage between the two phase is equal to the lamp voltage then the lamp will glow. When the voltage difference is big it will damage the lamp and when the difference is smaller the lamp will glow depending on the type of lamp.

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.

What are HRC fuses and where it is used? Which power plant has high load factor? 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. Mention the methods for starting an induction motor? The different methods of starting an induction motor. What is the difference between earth resistance and earth electrode resistance?

Only one of the terminals is evident in the earth resistance. In order to find the second terminal we should recourse to its definition: Earth Resistance is the resistance existing between the electrically accessible part of a buried electrode and another point of the earth, which is far away. The resistance of the electrode has the following components: A the resistance of the metal and that of the connection to it.

B the contact resistance of the surrounding earth to the electrode. Explain What is use of lockout relay in ht voltage? A lock-out relay is generally placed in line before or after the e-stop switch so the power can be shut off at one central location. This relay is powered by the same electrical source as the control power and is operated by a key lock switch.

The relay itself may have up to 24 contact points within the unit itself. This allows the control power for multiple machines to be locked out by the turn of a single key switch. What is the power factor of an alternator at no load? At no load Synchronous Impedance of the alternator is responsible for creating angle difference. So it should be zero lagging like inductor. Explain How to determine capacitor tolerance codes? Resolution:In electronic circuits, the capacitor tolerance can be determined by a code that appears on the casing.

The code is a letter that often follows a three-digit number such as Z. The first two are the 1st and 2nd significant digits and the third is a multiplier code. Most of the time the last digit tells you how many zeros to write after the first two digits and these are read as Pico-Farads. Resolution mA is a standard range used to indicate measured values for any process. The reason that 4ma is chosen instead of 0 mA is for fail safe operation.

For example- a pressure instrument gives output 4mA to indicate 0 psi, up to 20 mA to indicate psi, or full scale. Due to any problem in instrument i. So if range is mA then we can differentiate whether it is due to broken wire or due to 0 psi. Two bulbs of w and 40w respectively connected in series across a v supply which bulb will glow bright and why? What is meant by knee point voltage? Resolution:Knee point voltage is calculated for electrical Current transformers and is very important factor to choose a CT.

It is the voltage at which a CT gets saturated. CT-current transformer. What is reverse power relay? A generating stations is supposed to fed power to the grid and in case generating units are off,there is no generation in the plant then plant may take power from grid. To stop the flow of power from grid to generator we use reverse power relay. What will happen if DC supply is given on the primary of a transformer? Resolution:Mainly transformer has high inductance and low resistance. So high electrical current will flow through primary side of the transformer.

So for this reason coil and insulation will burn out. What is bus-bar? Resolution:Isolators are mainly for switching purpose under normal conditions but they cannot operate in fault conditions.

Actually they used for isolating the CBs for maintenance. Whereas CB gets activated under fault conditions according to the fault detected. Bus bar is nothing but a junction where the power is getting distributed for independent loads.

What are the advantage of free wheeling diode in a Full Wave rectifier? Resolution:It reduces the harmonics and it also reduces sparking and arching across the mechanical switch so that it reduces the voltage spike seen in a inductive load.

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. 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 generator. The motor generator set can used in the following different ways:. Define what is power quality meter?

Power Quality meters are common in many industrial environment. Small units are now available for home use as well. They give operators the ability to monitor the both perturbations on the power supply, as well as power used within a building, or by a single machine or appliance. In some situations, equipment function and operation is monitored and controlled from a remote location where communication is via modem, or highspeed communication lines. So we can understand the importance of power measurement through power quality meters.

What is the different between digital phase converter and ordinary phase converter? Digital phase converter are a recent development in phase converter technology that utilizes proprietary software in a powerful microprocessor to control solid state power switching components.

This microprocessor, called a digital signal processor DSP , monitors the phase conversion process, continually adjusting the input and output modules of the converter to maintain perfectly balanced three-phase power under all load conditions. Explain the operation of variable frequency transformer?

A variable frequency transformer is used to transmit electricity between two asynchronous alternating current domains. A variable frequency transformer is a doubly-fed electric machine resembling a vertical shaft hydroelectric generator with a three-phase wound rotor, connected by slip rings to one external ac power circuit. A direct-current torque motor is mounted on the same shaft.

Changing the direction of torque applied to the shaft changes the direction of power flow; with no applied torque, the shaft rotates due to the difference in frequency between the networks connected to the rotor and stator. The variable frequency transformer behaves as a continuously adjustable phase-shifting transformer. Heating and Welding Series-parallel Circuits Passive Filters Quantities and Units Series Circuits Branch, Loop and Node Analyses Alternating Current and Voltage Inductors RC Circuits RLC Circuits and Resonance Three-Phase Systems in Power Applications Time Response of Reactive Circuits