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EEE MCQ

A transformer transform-

20. A transformer transform-
A. Power
B. voltage
C. current
D. frequency


Note:
A transformer is a static electrical machine use for transforming power from one circuit to another without changing frequency.


Most Important Transformer MCQ, EEE MCQ, EEE Job Preparation, EEE Interview Tips, EEE BD, EEE BD Job MCQ, EEE BD Tips
EEE MCQ
Most Important Transformer MCQ

At relatively light load, transformer efficiency is low because-

19. At relatively light load, transformer efficiency is low because-
A. transformer losses are high
B. secondary output is low
C. fixed loss is high in proportion to the output
D. Cu loss is small


Note:
When a transformer designed to increase voltage from primary to secondary called step-up transformer and when it designed to reduce voltage from primary to secondary called step-down transformer.

Transformer turns ratio k=(n2/n1)=(v2/v1)=20.
v1=12 (voltage at primary)
therfore voltage at secondary (v2)=(k*v1)=(20*12)=240v.


Most Important Transformer MCQ, EEE MCQ, EEE Job Preparation, EEE Interview Tips, EEE BD, EEE BD Job MCQ, EEE BD Tips
EEE MCQ
Most Important Transformer MCQ

Which of the following is not a basic element of a transformer?

18. Which of the following is not a basic element of a transformer?
A. primary winding
B. secondary winding
C. mutual flux
D. core


Note:
There are three basic parts of a transformer, like
an iron core which serves as a magnetic conductor,
a primary winding and
a secondary winding.


Most Important Transformer MCQ, EEE MCQ, EEE Job Preparation, EEE Interview Tips, EEE BD, EEE BD Job MCQ, EEE BD Tips
EEE MCQ
Most Important Transformer MCQ

Transformers operating in parallel will share the load depending upon their-

17. Transformers operating in parallel will share the load depending upon their-
A. Rating
B. Per unit impedance.
C. Leakage reactance.
D. None of above


Note:
If two transformers connected in parallel operation with similar per unit impedances, they will mostly share the load of their KVA ratings.
The equivalent leakage impedance (ohms) should be inversely proportional to their respective KVA ratings. In other words, the per unit leakage impedance of the transformer based on their own KVA ratings must be equal. If per unit impedances are not same then, loading will not be in the ratio of their kVA ratings.


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EEE MCQ
Most Important Transformer MCQ

The input power under no load condition of transformer consists of

16. The input power under no load condition of transformer consists of
A. core losses and very small amount of copper loss in primary.
B. copper loss in transformers.
C. core loss in transformers.
D. None of above.


Note:
When the transformer is operating at no load, current in the secondary will be zero. While primary winding carries a small current I0 called no-load current which is 2 to 10% of the rated current. This current is responsible for supplying the iron losses (hysteresis and eddy current losses) in the core and a very small amount of copper losses in the primary winding.


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EEE MCQ
Most Important Transformer MCQ

When the turns ratio of a transformer is 20 and the primary ac voltage is 12 V, the secondary voltage is-

15. When the turns ratio of a transformer is 20 and the primary ac voltage is 12 V, the secondary voltage is-
A. 24v
B. 120v
C. 240v
D. 440v


Note:
When a transformer designed to increase voltage from primary to secondary called step-up transformer and when it designed to reduce voltage from primary to secondary called step-down transformer.

Transformer turns ratio k=(n2/n1)=(v2/v1)=20.
v1=12 (voltage at primary)
therfore voltage at secondary (v2)=(k*v1)=(20*12)=240v.


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EEE MCQ
Most Important Transformer MCQ

Does the transformer draw any current when secondary is open?

14. Does the transformer draw any current when secondary is open?
A. Yes
B. No


Note:
Since the secondary of the transformer is open, the primary draws only no-load current, which will have some copper loss. Therefore, power is no longer transferred from primary to secondary in this situation.


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EEE MCQ
Most Important Transformer MCQ

Which of the following is minimized by laminating the core of a transformer?

13. Which of the following is minimized by laminating the core of a transformer?
A. Eddy current.
B. Hysteresis loss.
C. Copper loss
D. Stray loss


Note:
Silicon Steel plays a very big role in laminated core-based transformers. as it increases the resistance and reduces the loss caused by eddy current.
As resistance of a material is inversely proportional to area of cross section (Resistance Law), the area of cross section can be decreased to increase resistance. So, in the case of a transformer we can decrease the area of the cross section by using the laminated sheets, by which the resistance gets increased, thus eddy currents can be reduced. Thus, the core of a transformer is laminated to reduce the Eddy Current.


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EEE MCQ
Most Important Transformer MCQ

Lamination of transformer core is made of

12. Lamination of transformer core is made of
A. cast iron
B. silicon steel.
C. cast steel
D. aluminium


Note:
The transformer core is made of silicon steel laminations which are insulated from each other by insulating varnish coating.


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EEE MCQ
Most Important Transformer MCQ

What is the condition for maximum efficiency of a transformer?

11. What is the condition for maximum efficiency of a transformer?
A. when copper loss = core loss
B. when transformer run by unity power factor
C. when copper loss = eddy current loss
D.when copper loss = hysteresis loss

Answer” লেখাতে ক্লিক করলে সঠিক উত্তরটি দেখাবে।
Click “Answer” for correct Answer.


Note:
The transformer will give the maximum efficiency when their copper loss is equal to the iron loss.
[Core loss is known as Iron loss]


Most Important Transformer MCQ, EEE MCQ, EEE Interview Tips, EEE BD, EEE BD Job MCQ, EEE BD Tips
EEE MCQ
Most Important Transformer MCQ

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