Transformer 11

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Objective Questions for Electrician and Wireman: Transformer 11

Subject: Transformer 11

Part 5: Objective questions and answers of Transformer


Q1. Single turn primary of a current transformer has a turn’s ratio 10:1. Which one of the following is the primary current if the current measured in secondary is 2 amperes?

a) 1 ampere

b) 5 ampere

c) 10 ampere

d) 20 ampere


Q2. In a transformer, if the number of turns in the secondary winding is twice that in the primary winding, the secondary voltage will be:

a) Half that of primary voltage

b) Same as the primary voltage

c) Twice the primary voltage

d) Four times the primary voltage


Q3. What is the full load current of 1 kva, 240v/120v single phase transformer at 0.8 p.f.?

a) 8.33 amps

b) 6.66 amps

c) 4.16 amps

d) 3.33 amps


Q4. As compared to an amplifier, a transformer cannot…….

a) Decrease the output power

b) Increase the output power

c) Increase the output current

d) Increase the output voltage


Q5. Small type transformer core for shell type generally used…….

a) E & i type of core

b) F & f type of core

c) E & e type of core

d) T & u type of core


Q6. When two transformers are operating in parallel, they will share the load depending upon their…….

a) Leakage reactance

b) Magnetizing current

c) Per unit impedance

d) Kva rating


Q7. The colour of silica gel in dry condition is:

a) Pink

b) Blue

c) Green

d) Red


Q8. Efficiency of transformers is determined by knowing its input and output power. Unit of power used for this purpose is kva/kw. What is the unit used for input and output when

calculating the all-day efficiency?

a) Kvar

b) Kw

c) Kva

d) Kwh


Q9. Secondary of a current transformer will have:

a) More turn of thick gauge

b) Less turn of thin gauge

c) More turn of thin gauge

d) Less turn of thick gauge


Q10. In constant voltage transformer at certain induced secondary voltage, the impedance of secondary winding will become equal to impedance of the capacitor across it. What is this condition of circuit known as?

a) Saturation

b) Equality

c) Good

d) Resonance


Q11. What principle makes the instrument transformer working?

a) Self-induction

b) Lenz's law

c) Mutual induction

d) Fleming's right hand rule


Q12. Current transformers are classified into five types. Which type of current transformer (c.t.) Principle is used in clip on or clamp on ammeter?

a) Oil immersed c.t.

b) Dry type c.t

c) Ring type c.t.

d) Wound type c.t.


Q13. When using a potential transformer, it should be connected to the:

a) Primary winding

b) Secondary winding

c) Low voltage winding

d) High voltage winding


Q14. You find a c.t. Of 10 : 1 ratio and p.t. Of 100: 1 ratio are available in the stores. ammeter of 0 to 5 amperes and voltmeter of 0 to 110 v are also available. The maximum high value of voltage and current that could be measured by using the above is….

a) 1100 v, 50 a

b) 11 kv, 50 a

c) 11 kv, 500 a

d) 110 kv, 500 a


Q15. The function of a breather in a transformer is…….

a) To provide protection against over current

b) To suppress harmonics

c) To arrest flow of moisture into the tank

d) To control the level of oil in the tank


Q16. You have to measure the current and voltage of a 3 phase circuit of 6.6 kv and load of 500 kva. In order to use a 5 a ammeter and 110 volts voltmeter, what is the ratio of ct and pt required?

a) Pt 60 : 1, ct 15 : 1

b) Pt 60 : 1, ct 50 : 1

c) Pt 1 : 60, ct 1 : 10

d) Pt 25 : 1, ct 100 : 1


Q17. The standard rated value of secondary current of current transformer as per is 2705  

(part i) -1981 shall be either:

 a) 5 ampere or 10 ampere

 b) 2.5 ampere or 5 ampere

 c) 1.5 ampere or 6 ampere

 d) 1 ampere or 5 ampere


Q18. The rated secondary voltage of a single phase potential transformer is:

a) 240 v

b) 230 v

c) 115 v

d) 110v


Q19. The input side of the single phase transformer is called as…….

a) 9Secondary side

b) Primary side

c) High voltage side

d) Low voltage side


Q20. Calculate the current in low voltage side of the 1 kva, 240 v/120 v single phase transformer.

a) 4.16 amperes

b) 6.72 amperes

c) 8.33 amperes

d) 9.12 amperes


Part 5: Objective questions and answers of Transformer


Q1. Answer d

Q2. Answer c

Q3. Answer a

Q4. Answer b

Q5. Answer a

Q6. Answer c

Q7. Answer b

Q8. Answer d

Q9. Answer c

Q10. Answer d

Q11. Answer c

Q12. Answer c

Q13. Answer b

Q14. Answer b

Q15. Answer c

Q16. Answer a

Q17. Answer d

Q18. Answer d

Q19. Answer b

Q20. Answer c

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