ABB Paper for B.tech / BE Engineering students held at Vadodara on 2 May, 2004
Technical Paper has 40 questions
Time Allowed is 45 minutes
ABB Electrical Engineering technical Multiple choice questions: Objective type questions:
(Note: In the questions on our website, we have tried our best to give the correct answers, but we dont assume any
responsibility for wrong information. You should
promptly check the answers and information provided)
(1) In a circuit, we are giving voltage of 50 Hz as well as 60. What will be the resultant frequency?
(a)less than 50 (b)more than 60(c)in between 50 & 60 (d)none
Answer will be none because if we apply two frequency component, we cant find resultant frequency with ease. Confirm the
2.In a circuit a single resistor is connected across a d.c. source, what will be the effect on current in first resistor if
we connect one more resistance in parallel with earlier one
Answer: There will be no change in current since it is a parallel combination of resistances.
3. Why we dont like flashover in transmission line (t-line)- (a ) Flashover may create earth fault (b) Flashover reduces the
life of insulator.
Read the flashover & puncture topics.
4. Total number of strands in a acsr conductor is 81, then what is the number of conductor in its outer layer.
(a)36 (b)18 (c)24…
5. Two questions based on p.u. calculation. P.U. calculation is given w.r.t an old base and we have to calculate it with
reference to new base. (new resistance/old)=(mva new /mva old)*(old voltage/new voltage)2.
A question is based upon transfer of p.u calculation in transformer i.e. How does the base change when we we move from
primary to secondary? Study this topic.
6. Which table is referred for sag calculation
(a)stringing chart.. answer
7. In a R-L ciruit an ac voltage is applied, such that instantaneous power is negative for 2ms, then what will be the power
(a) 9 deg, (b) 18 deg, (c) 36 Deg.
8. In an incandescent lamp
(a) luminous intensity is more than non-luminous intensity
Ans: Since efficiency is less than 100% answer is (b) (Confirm it)
9. In which motor no-load to full-load difference is lowest
(a) series motor (b) shunt motor (c) Compound motor
Ans: (b) The motor no load to full load difference is lowest in the shunt motor
10. In a 60Hz induction motor full load speed is 850 rpm then what is the Synchronous speed. (a) 900 rpm, (b) 950 rpm, (c)
Ans: (a) The synch speed will be 900 rpm
11. A synchronous Motor is running at synchronous Speed, if all of sudden D.C. excitation is removed, then
(a) it will rotate at slip speed, (b) it will stop, (c) it will continue to rotate at synchronous Speed
Ans: (a) The synch motor will rotate at slip speed because it will actually act as an Induction motor.
12. A transmission line is designed for 50Hz, 440KV. If we want to transfer power at 60Hz, 440 KV, then the power transfer
(a) decrease, (b) Increase, (c)None
Ans: (a) as P=( |Vt| |Ef| sin (delta) ) / X, where (delta) is torque angle.
13. Increased rotor resistance in rotor circuit of induction motor is related with
(a) high starting torque, (b) more speed variation,..
Answer:(a) The increased rotor resistance in rotor ckt of induction motor is related with high starting torque.
14. In the formulae E = 4.44 f N Ô, Ô is
(a) Avg value, (b) Rms value, (c) Maximum value….
Answer:(a) (confirm it)
15. Voltage & current in a circuit is given by V= V1+j V2 and I= I1 +j I2, then rms power is
……. (Refer book by Edministrator on NETWORK )
16. Input impedance of MOSFET is
(a) more than BJT. (Answer) The input impedance of MOSFET is more than that of BJT.
17, 18. Remember truth table of AND, NOR, NAND, OR, EX-OR ETC. The truth table related questions may be asked in any simple
way. (not much difficult if you know the truth table)
19. Conversion of Binary number into Equivalent decimal Number. Thats again very easy.
20. Megger is used for the measurement of (a) Insulation resistance, (b)
Answer: (a) Megger is used for insulation Res.
21. What is the Form factor for sinusoidal as well as DC
22. Formulae of Regulation (Vs- Vr)* 100/ Vr, then transmission line is
(a) short transmission line, (b) long, (c) medium…
Answer: (a) short trans. line.
23. Improvement in power factor reduces
(a) power consumed by consumer, (b) power generation, (c) both a & b..
Ans: (c) (Confirm it)
24. Question about field test of Series Motor..
25. No-load test for Synchronous motor, the graph is drawn
(a) stator open ckt emf Vs field
current.. (Answer: a)
26. An AC voltage of 50Hz is impressed in a resistive circuit, the oscillating power has a frequency (a) 50 Hz (b) 100 (c) no
oscillating power is there in resistive circuit.
27. Insulation used in transformer ____ leakage flux.
(a) increases, (b) decreases..
Ans: (b) It decreases leakage flux.
28. After rain what happens to Insulator (a) break-down strength of Insulator decreases, (b)Arch length reduces, .. Ans:
29.Diversity factor helps to …….
Related Important topics are:
Reserve capacity factor in depth, with some basic numerical part
30. Why capacitance is shown as a Shunt element in analysis of transmission line
(a) it is between Conductor & earth, (b) because Admittance is used for calculation of capacitive reactance.. Ans: (a)
31. B-R-Y sequence is followed in three phase system, if phase voltage in B-phase is Vm sin 100, then the phase voltage in
R-phase would be (a) Vm sin (-20)
32. In a particular circuit I = Im Sin (wt -270) and V = Vm Sin wt, then type of circuit is (a) pure resistive ckt
33. In a L-R circuit energy lost is 2000 W, the energy conserved is 500W, Find out the time constant.. Ans: Time constant =
L/R = 0.5
34. In electro-dynamometer Ammeter & wattmeter the type of scale is
35. For the same current carrying capacity corona loss of ACSR will be _____ than copper conductor.
(a) more, (b) less, (c) equal.
Ans:(b) Corona loss of ACSR will be less than the copper conductor.
36. A R-C circuit, supplied with DC, a bulb is connected across the Capacitor, then what happens to the illumination, if we
change the capacitance.
Ans: There is no change in the illumination if we change the capacitance.
37. Study about surge impendence of over-head and under-ground cable, Surge impedence formula = sqrt(L/C)
In some questions, we dont have all the options available so we are not mentioning all. All the options are quite close to
each other and confuse the candidate. Also confirm the options and soutions / answers given as they may not be correct.
Quantitative paper / PCM Physics Chemistry Maths paper questions
There are 45 Questions and the time allowed is 45 minutes
1. About 10 quantitative questions ( based on Mixture, Work etc. – easy )
2. What is GDP?
3. Vector algebra, condition for Co-planer vector
4. Gravitation, geo-synchronous satellite( height, orbit, radius ), escape velocity, how g (gravitational acc) varies, about
5. Basic electricity and Magnetism — Biot-savart law, current carrying conductor properties.
6. Nuclear physics, Bohr’s constant, and Other theories related .
7. Problem based on VIBGYOR , how wave length and frequency is varying.
8. Questions based on Plank’s Theory, E =hv
9. V=u + at , V2=u2 + 2as and W = mgh questions based on above theory
10. Faraday’s laws of electrolysis, m = Zit
11. Heat conduction problem.
12. Colour-coding of resistor (BBROYGBVGW)
(it can be remembered as given. THere are many ways and here is one:
BB ROY went to
Britain and he has a
Wife. Isnt it easy?
13. How the velocity of light changes in different mediums while frequency remains unchanged.
14. statistics, calculation of mode, co-efficient regression (3 – 4 Questions)
15. f(x) = Sin x + Cos x, find the maximum value of the function.. Answer: sqrt (2)
16. Formulae for parallel plate capacitor and force between plates.
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