Coal India Limited (CIL) Placement-Paper on March 15 2013 TYPICAL QUESTIONS & ANSWERS OBJECTIVE TYPE QUESTIONS Q.1 The two windings of a transformer is (A) conductively linked. (B) inductively linked. (C) not linked at all. (D) electrically linked. Ans : B Q.2 A salient pole synchronous motor is running at no load. Its field current is switched off. The motor will (A) come to stop. (B) continue to run at synchronous speed. (C) continue to run at a speed slightly more than the synchronous speed. (D) continue to run at a speed slightly less than the synchronous speed. Ans: B Q.3 The d.c. series motor should always be started with load because (A) at no load, it will rotate at dangerously high speed. (B) it will fail to start. (C) it will not develop high starting torque. (D) all are true. Ans: A Q.4 The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load speed is about (A) 50 Hz. (B) 20 Hz. (C) 2 Hz. (D) Zero. Ans: C Q.5 In a stepper motor the angular displacement (A) can be precisely controlled. (B) it cannot be readily interfaced with micro computer based controller. (C) the angular displacement cannot be precisely controlled. (D) it cannot be used for positioning of work tables and tools in NC machines. Ans: A Q.6 The power factor of a squirrel cage induction motor is (A) low at light load only. (B) low at heavy load only. (C) low at light and heavy load both. (D) low at rated load only. Ans: A Q.7 The generation voltage is usually (A) between 11 KV and 33 KV. (B) between 132 KV and 400 KV. (C) between 400 KV and 700 KV. (D) None of the above. Ans: A Q.8 When a synchronous motor is running at synchronous speed, the damper winding produces (A) damping torque. (B) eddy current torque. (C) torque aiding the developed torque. (D) no torque. Ans: D Q.9 If a transformer primary is energised from a square wave voltage source, its output voltage will be (A) A square wave. (B) A sine wave. (C) A triangular wave. (D) A pulse wave. Ans: A Q.10 In a d.c. series motor the electromagnetic torque developed is proportional to Q.11 In a 3 – phase induction motor running at slip ‘s’ the mechanical power developed in terms of air gap power Pg is Q.12 In a 3 – phase induction motor the maximum torque Q.13 In a d.c. machine, the armature mmf is (A) stationary w.r.t. armature. (B) rotating w.r.t. field. (C) stationary w.r.t. field. (D) rotating w.r.t. brushes. Ans: C Q.14 In a transformer the voltage regulation will be zero when it operates at (A) unity p.f. (B) leading p.f. (C) lagging p.f. (D) zero p.f. leading. Ans: B Q.15 The maximum power in cylindrical and salient pole machines is obtained respectively at load angles of Q.16 The primary winding of a 220/6 V, 50 Hz transformer is energised from 110 V, 60 Hz supply. The secondary output voltage will be (A) 3.6 V. (B) 2.5 V. (C) 3.0 V. (D) 6.0 V. Ans: C Q.17 The emf induced in the primary of a transformer (A) is in phase with the flux. (B) lags behind the flux by 90 degree. (C) leads the flux by 90 degree. (D) is in phase opposition to that of flux. Ans: C Q.18 The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for a (A) dc machine. (B) 3 phase induction machine. (C) synchronous machine. (D) single phase induction machine. Ans: all options are correct Q.19 The current from the stator of an alternator is taken out to the external load circuit through (A) slip rings. (B) commutator segments. (C) solid connections. (D) carbon brushes. Ans: C Q.20 A motor which can conveniently be operated at lagging as well as leading power factors is the (A) squirrel cage induction motor. (B) wound rotor induction motor. (C) synchronous motor. (D) DC shunt motor. Q.21 A hysteresis motor (A) is not a self-starting motor. (B) is a constant speed motor. (C) needs dc excitation. (D) can not be run in reverse speed. Ans: B Q.22 The most suitable servomotor for low power applications is (A) a dc series motor. (B) a dc shunt motor. (C) an ac two-phase induction motor. (D) an ac series motor. Ans: B Q.23 The size of a conductor used in power cables depends on the (A) operating voltage. (B) power factor. (C) current to be carried. (D) type of insulation used. Ans: C Q.24 Out of the following methods of heating the one which is independent of supply frequency is (A) electric arc heating (B) induction heating (C) electric resistance heating (D) dielectric heating Ans: C Q.25 A two-winding single phase transformer has a voltage regulation of 4.5% at full-load nand unity power-factor. At full-load and 0.80 power-factor lagging load the voltage regulation will be (A) 4.5%. (B) less than 4.5%. (C) more than 4.5%. D) 4.5% or more than 4.5%. Ans: C Q.26 In a dc shunt motor the terminal voltage is halved while the torque is kept constant. The resulting approximate variation in speed 'ω' and armature current I' ' a will be (A) Both ω and aI are doubled. (B) ω is constant and a I is doubled. (C) ω is doubled while a I is halved. (D) ω is constant but Ans: B Q.27 A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole, induction motor. When the motor is delivering rated output, the slip is found to be 0.05. The speed of the rotor m.m.f. relative to the rotor structure is (A) 1500 r.p.m. (B) 1425 r.p.m. (C) 25 r.p.m. (D) 75 r.p.m. Ans: D NS = 120f /P = 120 x 50 /4 =1500rpm N = NS ( 1-s) = 1500 (1-0.05) = 1425 ∴relative speed = 1500 – 1425 = 75 rpm Q.28 An alternator is delivering rated current at rated voltage and 0.8 power-factor lagging case. If it is required to deliver rated current at rated voltage and 0.8 power-factor leading, the required excitation will be (A) less. (B) more. (C) more or less. (D) the same. Ans: B Q.29 A ceiling fan uses (A) split-phase motor. (B) capacitor start and capacitor run motor. (C) universal motor. (D) capacitor start motor. Ans: D To give starting torque and to maintain speed. Q.30 A stepper motor is (A) a dc motor. (B) a single-phase ac motor. (C) a multi-phase motor. (D) a two phase motor. Ans: D Stepper motor works on 1-phase-ON or 2-phase –ON modes of operation Q.31 The ‘sheath’ is used in cable to (A) provide strength to the cable. B) provide proper insulation. (C) prevent the moisture from entering the cable. (D) avoid chances of rust on strands. Ans: A The sheath in underground cable is provided to give mechanical strength. Q.32 The drive motor used in a mixer-grinder is a (A) dc motor. (B) induction motor. (C) synchronous motor. (D) universal motor. Ans: D Q.33 A 1:5 step-up transformer has 120V across the primary and 600 ohms resistance across the secondary. Assuming 100% efficiency, the primary current equals (A) 0.2 Amp. (B) 5 Amps. (C) 10 Amps. (D) 20 Amps. Ans: A I1= V1 /R1 = 120/600 = 0.2 (η = 100%, losses are zero ∴V1 = VR = I1R1) Q.34 A dc shunt generator has a speed of 800 rpm when delivering 20 A to the load at the terminal voltage of 220V. If the same machine is run as a motor it takes a line of 20A from 220V supply. The speed of the machine as a motor will be (A) 800 rpm. (B) more than 800 rpm. (C) less than 800 rpm. (D) both higher or lower than 800 rpm. Ans: C Ng= Eg (60A / Φpz) Eg = V + Ia Ra ; in generator Nm= Eb (60A / Φpz) Eb = V - Ia Ra ; in motor Eg > E b for same terminal voltage Therefore, Ng > N m Q.35 A 50 Hz, 3-phase induction motor has a full load speed of 1440 r.p.m. The number of poles of the motor are A) 4. (B) 6. (C) 12. (D) 8. 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 Nswill 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 Q. 36 In a 3-phase synchronous motor (A) the speed of stator MMF is always more than that of rotor MMF. (B) the speed of stator MMF is always less than that of rotor MMF. (C) the speed of stator MMF is synchronous speed while that of rotor MMF is zero. (D) rotor and stator MMF are stationary with respect to each other. Ans: D Because, Motor is magnetically locked into position with stator, the rotor poles are engaged with stator poles and both run synchronously in same direction Therefore, rotor & stator mmf are stationary w.r.t each other. Q.37 In a capacitor start single-phase induction motor, the capacitor is connected (A) in series with main winding. (B) in series with auxiliary winding. (C) in series with both the windings. (D) in parallel with auxiliary winding. Ans: B To make single phase motor self start. We split the phases at 90 degree. Hence, motor behaves like a two phase motor. Q.38 A synchro has (A) a 3-phase winding on rotor and a single-phase winding on stator. (B) a 3-phase winding on stator and a commutator winding on rotor. (C) a 3-phase winding on stator and a single-phase winding on rotor. (D) a single-phase winding on stator and a commutator winding on rotor. Ans: C Synchros : The basic synchro unit called a synchro transmitter. It’s construction similar to that of a Three phase alternator. Q.39 As the voltage of transmission increases, the volume of conductor (A) increases. (B) does not change. (C) decreases. (D) increases proportionately. Ans: C Decreases due to skin effect.

1. A certain type of mixture is prepared by mixing brand A at Rs.9 a kg. with brand B at Rs.4 a kg. If the mixture is worth Rs.7 a kg., how many kgs. of brand A are needed to make 40kgs. of the mixture? Ans. Brand A needed is 24kgs. 2. A wizard named Nepo says “I am only three times my son’s age. My father is 40 years more than twice my age. Together the three of us are a mere 1240 years old.” How old is Nepo? Ans. 360 years old. 3. One dog tells the other that there are two dogs in front of me. The other one also shouts that he too had two behind him. How many are they? Ans. Three. 4. A man ate 100 bananas in five days, each day eating 6 more than the previous day. How many bananas did he eat on the first day? Ans. Eight. 5. If it takes five minutes to boil one egg, how long will it take to boil four eggs? Ans. Five minutes. 6. Three containers A, B and C have volumes a, b, and c respectively; and container A is full of water while the other two are empty. If from container A water is poured into container B which becomes 1/3 full, and into container C which becomes 1/2 full, how much water is left in container A? 7. ABCE is an isosceles trapezoid and ACDE is a rectangle. AB = 10 and EC = 20. What is the length of AE? Ans. AE = 10. 8. A Rectangular room had width half of its lengdth. When 6 is decreased from both length and width then its area is differed by 108 so find the width Ans:l=8 9 Three cards are drawn at random from an ordinary pack of cards. Find the probability that they will consist of a king, a queen and an ace. Ans. 64/2210. 10. A number of cats got together and decided to kill between them 999919 mice. Every cat killed an equal number of mice. Each cat killed more mice than there were cats. How many cats do you think there were ? Ans. 991. 11. If Log2 x – 5 Log x + 6 = 0, then what would the value / values of x be? Ans. x = e2 or e3. 12. The square of a two digit number is divided by half the number. After 36 is added to the quotient, this sum is then divided by 2. The digits of the resulting number are the same as those in the original number, but they are in reverse order. The ten’s place of the original number is equal to twice the difference between its digits. What is the number? Ans. 46 13.Can you tender a one rupee note in such a manner that there shall be total 50 coins but none of them would be 2 paise coins.? Ans. 45 one paisa coins, 2 five paise coins, 2 ten paise coins, and 1 twenty-five paise coins. 14.A monkey starts climbing up a tree 20ft. tall. Each hour, it hops 3ft. and slips back 2ft. How much time would it take the monkey to reach the top? Ans.18 hours. 15. What is the missing number in this series? 8 2 14 6 11 ? 14 6 18 12 Ans. 9 16. The minute hand of a clock overtakes the hour hand at intervals of 64 minutes of correct time. How much a day does the clock gain or lose? Ans. 32 8/11 minutes. 17. Solve for x and y: 1/x – 1/y = 1/3, 1/x2 + 1/y2 = 5/9. Ans. x = 3/2 or -3 and y = 3 or -3/2. 18. Daal is now being sold at Rs. 20 a kg. During last month its rate was Rs. 16 per kg. By how much percent should a family reduce its consumption so as to keep the expenditure fixed? Ans. 20 %. 19. Find the least value of 3x + 4y if x2y3 = 6. Ans. 10. 20. Can you find out what day of the week was January 12, 1979? Ans. Friday. 21. A garrison of 3300 men has provisions for 32 days, when given at a rate of 850 grams per head. At the end of 7 days a reinforcement arrives and it was found that now the provisions will last 8 days less, when given at the rate of 825 grams per head. How, many more men can it feed? Ans. 1700 men. 22. From 5 different green balls, four different blue balls and three different red balls, how many combinations of balls can be chosen taking at least one green and one blue ball? Ans. 3720. 23. Three pipes, A, B, & C are attached to a tank. A & B can fill it in 20 & 30 minutes respectively while C can empty it in 15 minutes. If A, B & C are kept open successively for 1 minute each, how soon will the tank be filled? Ans. 167 minutes. 24. A person walking 5/6 of his usual rate is 40 minutes late. What is his usual time? Ans. 3 hours 20 minutes. 25. Mr. Shah decided to walk down the escalator of a tube station. He found that if he walks down 26 steps, he requires 30 seconds to reach the bottom. However, if he steps down 34 stairs he would only require 18 seconds to get to the bottom. If the time is measured from the moment the top step begins to descend to the time he steps off the last step at the bottom, find out the height of the stair way in steps? Ans.46 steps.

1. What should come in the place of (?) in the given series? ACE, FGH, ?, PON (A) KKK (B) JKI (C) HJH (D) IKL Ans. (A) 2. Typist : Typewriter : : Writer: ? (A) Script (B) Pen (C) Paper (D) Book Ans. (B) 3. Paint: Artist : : Wood: ? (A) Furniture (B) Forest (C) Fire (D) Carpenter Ans. (D) 4. acme : mace :: alga: ? (A) glaa (B) gaal (C) laga (D) gala Ans. (D) 5. EIGHTY : GIEYTH : : OUTPUT:? (A) UTOPTU (B) UOTUPT (C) TUOUTP (D) TUOTUP Ans. (D) 6. ‘Medicine’ is related to ‘Patient’ in the same way as ‘Education’ is related to— (A) Teacher (B) School (C) Student (D) Tuition Ans. (C) 7. Fill in the missing letter in the following series— S, V, Y, B, ? (A) C (B) D (C) E (D)G Ans. (C) 8. What should come in the place of question mark in the following series? 3, 8, 6, 14, ?, 20 (A) 11 (B) 10 (C) 8 (D) 9 Ans. (D) 9. Select the correct option in place of the question mark. AOP, CQR, EST, GUV, ? (A) IYZ (B) HWX (C) IWX (D) JWX Ans. (C) 10. What should come in the place of question mark in the following series? 1, 4, 9, 25, 36, ? (A) 48 (C) 52 (B) 49 (D) 56 Ans. (B) Directions—(Q. 11 to 14): Select the one which is different from the other three. 11. (A) Bokaro (B) Jamshedpur (C) Bhilai (D) Agra Ans. (D) 12. (A) January (B) February (C) July (D) December Ans. (B) 13. (A) Bible (B) Panchsheel (C) Geeta (D) Quran Ans. (B) 14. (A) Star (B) Sun (C) Sky (D) Moon Ans. (C) Coal India Limited Alphabet Qquestions Directions—(Q. 15 to 17): based on alphabets. 15. If the sequence of the alphabets is reversed which of the following would be the 14th letter from your left? (A) N (B) L (C) O (D) None of these Ans. (D) 16. Which letter is the 8th letter to the right of the letter, which is 12th from the left? (A) V (B) T (C) W (D) Y Ans. (B) 17. Which letter is the 8th letter to the right of the letter which is 10th to the left of the last but one letter from the right? (A) V (B) X (C) W (D) I Ans. (C) Directions—(Q. 18 to 23) Three of the following four are alike in a certain way and so form a group. Which is the one that does not belong to that group? 18. (A) Green (B) Red (C) Colour (D) Orange Ans. (C) 19. (A) Rabbit (B) Crocodile (C) Earthworm (D) Snail Ans. (A) 20. (A) Polo (B) Chess (C) Ludo (D) Carrom Ans. (A) 21. (A) Sun (B) Universe (C) Moon (D) Star Ans. (B) 22. (A) Cheese (B) Milk (C) Curd (D) Ghee Ans. (B) 23. (A) Carrot (B) Radish (C) Potato (D) Brinjal Ans. (D) 24. In a certain code ‘CONTRIBUTOR’ is written as ‘RTNOCIROTUB’. How is ‘prohibition’ written in that code? (A) NOITIBIHORP (B) IHORPBITION (C) ITIONBIHOTP (D) IHORPBNOITI Ans. (D) 25. If ‘CAT’ and ‘BOAT’ are written as XZG and ‘YLZG’ respectively in a code language how is ‘EGG’ to be written in the same language? (A) VSS (B) URR (C) VTT (D) UTF Ans. (C)