Electrical Engineering MCQ Question Papers: Campus Placement

Subject: Electrical Machine 8

**Part 2: List for questions and answers of Electrical Machine II**

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**Q1.In a 20 kVA, 2200 / 220 volts transformer iron and copper losses are 300 and 400 watts ****respectively. Its efficiency at half load and unity power factor is?**

**a) 95.11%**

**b) 96.15%**

**c) 97.77%**

**d) 98%**

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**Q2.A 600 kVA transformers have iron losses of 400 kW and copper losses of 500 kW. Its kVA ****rating for maximum efficiency is given by?**

**a) 537 kVA**

**b) 548 kVA**

**c) 555 kVA**

**d) 585 kVA**

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**Q3.If the power factor of a transformer increases, then its efficiency will ?**

**a) Increases**

**b) Decreases**

**c) Remains constant**

**d) Not related to each other**

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**Q4. For maximum efficiency in a transformer?**

**a) Core losses = 2 * copper losses**

**b) Core losses = copper losses / 2**

**c) Core losses = copper losses**

**d) Core losses = copper losses ****?**** 2**

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**Q5. What happens to the hysteresis losses and eddy current losses, if the frequency of a ****transformer is increased keeping the supply voltage constant? ?**

**a) Both will decrease**

**b) Hysteresis losses will increase and eddy current losses will decrease**

**c) Hysteresis losses will remain same and eddy current losses will decrease**

**d) Hysteresis losses will decrease and eddy current losses will remain same **

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**Q6.If the applied voltage is increased by 10% and the applied frequency is increased by 20% ****of a single phase transformer, the percentage change in eddy current losses will be ?**

**a) 19%**

**b) 20%**

**c) 21%**

**d) 40%**

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**Q7.In the design of transformer, higher flux density is used. Due to which ?**

**a) weight per kVA increases**

**b) weight per kW increases**

**c) weight per kW decreases**

**d) weight per kVA decreases**

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**Q8.For a single phase no load transformer, which among the following losses will be ****minimum??**

**a) hysteresis losses**

**b) eddy current losses**

**c) copper losses**

**d) mechanical losses**

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**Q9.If the voltage supply of a single phase transformer is doubled and the supply frequency is ****halved, then the eddy current loss will become ?**

**a) remains same**

**b) double of the original**

**c) four times of original**

**d) half of the original**

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**Q10.If the supply voltage is kept at constant value and the supply frequency is increased. ****The magnetizing and core loss component?**

**a) Both will decrease**

**b) Magnetizing component will increase and core loss will decrease**

**c) Magnetizing component will decrease and core loss will increase**

**d) Both will increase **

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**Q11.If the applied voltage of a certain transformer is increased by 50% keeping the ****frequency constant, the maximum flux density will become?**

**a) Remains same**

**b) 1.5 times the original value**

**c) Double the original value**

**d) Half of the original value**

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**Q12. If the power factor of load is near unity and leading, the full load voltage regulation of ****a power transformer will be ?**

**a) Zero**

**b) One**

**c) 0.5**

**d) 0.707**

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**Q13.When a resistance is to be transferred from primary to secondary side of transformer ****with the turns ratio as k, it must be?**

**a) Multiplied by k ****?**** 2**

**b) Multiplied by k**

**c) Divided by k**

**d) Divided by k ****?**** 2**

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**Q14.For an ideal transformer winding resistances and leakage flux should be ?**

**a) Least, maximum**

**b) Both should be maximum**

**c) Both should be zero**

**d) Maximum, least**

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**Q15.If V1 is the primary applied voltage and E1 is the primary induced emf. For an ideal ****transformer?**

**a) V1 > E1**

**b) V1 = E1**

**c) V1 less than E1**

**d) V1 = E1 / 2**

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**Q16.A transformer is said to be isolation transformer if its primary to secondary ratio is?**

**a) Equal to one**

**b) More than one**

**c) Less than one**

**d) Equal to 0.5 **

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**Q17.If the primary winding is excited by a purely sinusoidal alternating voltage, than the ****nature of the flux produced is?**

**a) Square wave**

**b) Rectangular wave**

**c) Saw tooth wave**

**d) Sinusoidal wave**

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**Q18.For the calculation of induced emf in a transformer the flux used in the equation is in its ****?**

**a) RMS value**

**b) Average value**

**c) Maximum value**

**d) Double of its maximum value**

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**Q19.In a transformer tank, grounding is given to protect it from lightening stoke. Grounding ****lug is usually installed near?**

**a) Bottom of the tank**

**b) Top of the tank**

**c) In the middle of the tank**

**d) Anywhere on the tank**

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**Q20.The globules of water present in oil may result directly in a breakdown. This can be ****prevented by?**

**a) Proper insulation**

**b) Isolation of oil from air by using an inert gas**

**c) Heating the tank**

**d) None of these **

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**Part 2: List for questions and answers of Electrical Machine II**

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**Q1. Answer: b**

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**Q2. Answer: a**

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**Q3. Answer: a**

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**Q4. Answer: c**

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**Q5. Answer: d**

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**Q6. Answer: c**

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**Q7. Answer: d**

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**Q8. Answer: d**

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**Q9. Answer: c**

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**Q10. Answer: d**

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**Q11. Answer: b**

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**Q12. Answer: a**

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**Q13. Answer: a**

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**Q14. Answer: c**

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**Q15. Answer: b**

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**Q16. Answer: a**

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**Q17. Answer: d**

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**Q18. Answer: c**

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**Q19. Answer: a**

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**Q20. Answer: b**