Recent questions and answers in Electrical Engineering

Description : An Auto-transformer (which has only one winding) may be used as a ______ .  (A) Both Step-Up and Step-Down transformer (B) Step-Down Transformer (C) Step-Up Transformer (D) None of these

Last Answer : An auto-transformer may be used as: A. Both Step-Up and Step-Down transformer An auto-transformer is a type of transformer that has only one winding and can be used as a step-up or ... size. Therefore, an auto-transformer is a versatile transformer that can be used for a variety of applications.

Description : If a 220 V heater is used on 110 V supply, the heat produced by it will be nearly (a) one half (b) twice (c) one-fourth (d) four times 

Last Answer : If a 220 V heater is used on a 110 V supply, the heat produced by it will be significantly less than it would be if it were used on a 220 V supply. This is because the heater is designed to operate ... the heater, but it will be significantly less than it would be if it were used on a 220 V supply.

Description : Equivalent π model is quite suitable for analyzing the performance of transmission line of  A) 50 km length B) 150 km length C) 250 km length D) All of the above lengths

Last Answer : 150km because nominal π and T method are used in medium transmission lines . and these lines ranges from 80-240 km

Description : Varley loop tests are preferred over Murray loop tests because  (1) Valley loop test can locate open circuit fault (2) Varley loop test gives higher accuracy (3) in Varley loop test provision is made for ... of obtaining it from the relation R = pl/a (4) Valley loop test can locate the earth fault

Last Answer : Option 3

Description : A 1mA D' Arsonval movement has resistance of 100 Ω. It is to be converted to a 10 V voltmeter. The value of multiplier resistance is  (A) 999 Ω (B) 9999 Ω (C) 9900 Ω (D) 990 Ω 

Last Answer : C) Rs = (10/1x10^-3) - 100 Rs = 9900

Description : Minimum distance of underground cable from the foundation of building should be   (a) 100 cm (b) 50 cm (c) 10 cm (d) 5 cm 

Last Answer : A

Description : Define reluctance and give its unit.

Last Answer : Reluctance is the resistance offered the material to the passage of magnetic flux through it and corresponds to resistance in the electric circuit it is denoted by (s) And it's unit is amper per weber (A/Wb)

Description : In a CRO, the quantity to be measured is applied across  (1) focusing electrodes (2) cathode (3) Y-plates (4) X-plates

Last Answer : C

Last Answer : e

Last Answer : YEETUS FEETUS

Description : A. active power B. reactive power C. apparent power D. A & C E. B & C

Last Answer : D

Description : CRO is used to measure ________. A. Amplitude B. Phase difference C. Frequency D. All of these 

Last Answer : D

Description : Short-circuit kVA is obtained by multiplying the base kVA by (1) 10% X (2) 20% X (3) 50% X (4) 100% X

Last Answer : 100%

Description : Consider the following statements : If a high Q parallel resonant circuit is loaded with a resistance  1. The circuit impedance reduces.  2. The resonant frequency remains the same.  3. The bandwidth reduces.  Which of the above statements is/are correct ?

Last Answer : 1

Description : The voltage of a circuit is measured by a voltmeter having input impedance comparable with the output impedance of the circuit thereby causing error in voltage measurement. This error may be called as_________.

Last Answer : error caused by misuse of instrument

Last Answer : 2

Description : Define Electrolyte. Write its types. 

Last Answer : A substance that dissociates into ions in solution and acquires the capacity to conduct electricity. Sodium, potassium, chloride, calcium, and phosphate are examples of electrolytes, informally known as lytes.

Description : Arc welding uses following electric supply (A) ac (B) dc (C) both ac and dc (D) spiral waveform 

Last Answer : both ac and dc

Description : Which of the following is true with an auto transformer? A) It has only one winding  B) It has two separate windings namely primary winding and secondary winding C) It has two primary windings and one single secondary winding D) None of these

Last Answer : A it has only one winding.

Description : A megger is basically a/an   (a) Moving iron type instrument (b) Moving coil type instrument (c) Hot wire instrument (d) Electrolytic instrument

Last Answer : Moving coil type instrument

Description : A megger is to measure insulation resistance of a cable. The cable should be connected to   (a) Battery (b) DC supply (c) AC supply (d) No supply  

Last Answer : majorly in DC as well as AC......but ans is Battery

Description : what is the difference between four point starter and three point starter?

Last Answer : The shunt connection in four point starter is provided separately form the line where as in three point starter it is connected with line which is the drawback in three point starter.

Description : Why a dc series motor has a high starting torque?

Last Answer : motor

Description : What is the principle of DC motor?

Last Answer : principle

Description : If a ferromagnetic material is heated upto Curie temperature, it becomes (a) Permanent magnet (b) Anti-ferromagnetic material (c) Diamagnetic material (d) Paramagnetic material 

Last Answer : Paramagnetic material

Description : Describe capacitive type proximity switch with neat diagram.

Last Answer : Its a type of a switch controlled by action of storing energy and then releasing it.

Description : Aluminium conductor cables can be joined by   (a) Gas welding (b) Soldering (c) Compression (d) Thermit welding

Last Answer : welding

Description : The most suitable material for transformer core is  (1) hot rolled grain oriented steel (2) cold rolled grain oriented steel (3) aluminium (4) copper

Last Answer : cold rolled grain oriented steel

Description : A large dc motor is required to control the speed of the blower from a 3 -phase ac source. The suitable ac to dc converter is, 3 -phase (a) Fully controlled bridge converter ( ... bridge converter with freewheeling diode (c) Half controlled bridge converter (d) Converter pair in sequence control

Last Answer : a fullu control

Description : A three phase transmission line delivers a load of 5 MW at 0.8 power factor lagging. Resistance of each conductor is 0.5 ohm / km. Receiving end voltage is 33 kV. If the line loss is not to exceed 10%, determine the length of the line.  (A) 7 km (B) 27.9 km (C) 56.8 km (D) 13.9 km

Last Answer : B

Description : Stranded wires are mainly used to   (a) reduce skin effect (b) reduce metal fatigue (c) reduce proximity effect (d) both (b) and (c)

Last Answer : B

Description : A 60 Hz, 4 pole turbo generator rated 100 MVA, 13.8 KV has an inertia constant of 10 MJ/MVA. Find the stored energy in the rotor at synchronous speed.  (A) 10 MJ (B) 100 J (C) 1000 J (D) 1000 MJ 

Last Answer : c

Description : The number of parallel paths in armature winding of four pole wave winding connected dc machine having 22 coil sides is (1) 4 (2) 22 (3) 2 (4) 11 

Last Answer : Ans- Option (3) because wave winding always have 2 parallel paths

Description : A single phase 60 Hz generator supplies an inductive load of 4500kW at a power factor of 0.80 lagging by means of a 20 km long overhead transmission line. The line resistance and inductance are 0.0195 ohm and 0.60 mH ... voltage regulation of the line.  (A) 12.59% (B) 16.34% (C) 32.68% (D) 41.15% 

Last Answer : Answer is C

Description : A 50 Hz, 3—phase induction motor has a full load speed of 1440 rpm. The number of poles of the motor is:   (A)4 (8)6 (0)12  (D)8

Last Answer : Ans: A N= Ns (1-S) = NS –NS x S 1440 = Ns (1-S) Ns = 1440 / (1-S) Ns = (120 f/ p) = 120 x 50/p = 6000 p Ns will be closer to N i.e 1440 When P=2 ; Ns = 3000 rpm , not close to N When P=4 ; Ns = 1500 rpm , it is closer to N Therefore P =4 for N=1440

Description : Transformer voltage is maximum when two coils are (1) Normal to each other (2) Aligned along the same axis (3) 600 away from each other (4) 2700 away from each other

Last Answer : 2

Description : Earth resistance comprises of   A. Resistance of soil away from electrode.   B. Contact resistance between electrode and soil.   C. Resistance of metal electrode   (a) A only  (b) A and B only   (c) A and C only  (d) A, B and C together 

Last Answer : D

Description : RMS value of rectangular wave of period T, having a value of +V for a duration T1(

Last Answer : a

Description : A 200 V, 50 Hz inductive circuit takes a current of 10 A at 30 degree lagging pf, what is the inductive reactance of the circuit?  (A) 17.8 Ω (B) 100 Ω (C) 178 Ω (D) 10 Ω 

Last Answer : D

Description : The r.m.s. value of a sinusoidal A.C. current is equal to its value at an angle of______degrees.

Last Answer : 45

Description : The function(s) of pole shoes in DC machine is/ are to : -  a) Support the field coils b) Reduce the reluctance of the magnetic path c) Spread out the flux to achieve uniform flux distribution in the air gap d) All of the above.

Last Answer : Support the field coils

Description : The power in a 3phase circuit is measured with the help of 2 wattmeters. The reading of one of wattmeters is positive and that of the others is negative. The magnitude of readings is different. It can be concluded that the ... (A) Unity (B) 2 (lagging) (C) 5 (lagging) (D) Less than 0.5 (lagging)

Last Answer : A

Description : During 3-phase short circuit on a unloaded alternator, the dc component may be zero in (1) One phase only (2) Any two phases (3) All three phases (4) None of the above 

Last Answer : 1

Description : A single phase energy meter has a constant of 1200 revolution/kWh. When a load of 200 W is connected, the disc rotates at 4.2 revolutions per min. If the load is on for 10 hours, the meter records an excess of   (a) 0.1 kWh (b) 0.2 kWh (c) 1.0 kWh (d) 2.0 kWh 

Last Answer : 2

Description : Lissajous pattern obtained on a CRO screen is a circle. Frequency of two signals are   (a) Equal (b) Unequal (c) Zero (d) Infinity 

Last Answer : a

Description : Change in the circuit voltage will affect   (a) Resonant frequency (b) Q factor (c) Current (d) Bandwidth  

Last Answer : C

Description : List any four advantages of 3-phase systems over 1 -phase systems.

Last Answer : .if you miss one phase u get the remaining two .3phase machines are an added advantage . expensive but reliable .More output

Description : Define power factor. State its significance. What is the condition for unity power factor ? 

Last Answer : Definition of Power factor: Power factor is cosine of angle between voltage and current.  OR Power factor is the ratio of active power to the apparent power .  Significance of Power factor:  ... When cosine of angle between voltage and current is zero. When R = Z  When KW = KVA 

Description : Calculate the equivalent resistance between A & B using star-delta conversion

Last Answer : Solution :  Converting Inner star in to delta-  Resistances 4 and 6 are in parallel in all branch so

Description : State different types of power in ac circuits. Write the expression and units for the same. Draw the power triangle. 

Last Answer : i) Active Power (P):- The active power is defined as the average power Pavg taken by or consumed by the given circuit.   ii) Reactive Power (Q):-  The reactive power is defined as the product of ... values of voltage (v) and current (I) it is given by    iv) Power Triangle: