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In a transformer the resistance between its primary and secondary should be?

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In a transformer the resistance between its primary and secondary should be infinity.

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Description : Define: primary and secondary distribution system 

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Answer : Primary winding of a transformer could either be a low voltage or high voltage winding.

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Answer : The secondary of a current transformer is always short-circuited under operating conditions because it avoids core saturation and high voltage induction.

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Description : What is the mathematical relationship between resistance and conductance?

Description : What is the relationship between power and resistance?

Answer : P = I2R Where P = power I = Current R = Resistance

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Description : What happens to the voltage in the secondary when the frequency of the supply in the primary is decreased? A) It increases B) It decreases C) It remains the same D) Cannot say unless the actual percentage increase in the frequency is known

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Description : Primary and Backup Protection

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Answer : The chemical used in breather for transformer should have the quality of cleansing the transformer oil.

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Description : What is the definition of a primary instrument?

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Description : State the meaning of secondary instrument. Classify secondary instruments.

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Answer : CT secondary should never be kept open because it will cause saturation of the core to a high level and very high voltage will appear across the secondary which can breakdown the insulation. One terminal of PT secondary is always grounded to avoid capacitive induction and for human safety

Description : Which of the following connection of transformers will give highest value of secondary voltage ? (A) Delta primary delta secondary (B) Delta primary star secondary (C) Star primary star secondary (D) Star primary delta secondary

Answer : Which of the following connection of transformers will give highest value of secondary voltage ? (A) Delta primary delta secondary (B) Delta primary star secondary (C) Star primary star secondary (D) Star primary delta secondary

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Answer : The instruments which will give the direct readings are called secondary instruments

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Answer : The maximum load that a power transformer can carry is limited by its voltage ratio.

Description : When measuring insulation resistance of cables using d.c. source, the galvanometer used should be initially short circuited because  (A) Cables have a low value of capacitance which draws a high ... high value of charging current (D) Cables have a low value of capacitance and initial resistance

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Answer : Ideal resistance of ammeter should be zero.

Description : Consider a cube of material of sides 1 cm with a resistance of 0.003 Ω between its opposite faces. What is the resistance if the same volume of the material is drawn into a length of 50 cm with a uniform cross – section? A) 0.003 Ω B) 0.15 Ω C) 7.5 Ω D) None of these

Answer : Consider a cube of material of sides 1 cm with a resistance of 0.003 Ω between its opposite faces. What is the resistance if the same volume of the material is drawn into a length of 50 cm with a uniform cross – section? A) 0.003 Ω B) 0.15 Ω C) 7.5 Ω D) None of these

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Description : What do you mean by exciting resistance and exciting reactance?

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Description : The dielectric strength of transformer oil is expected to be?

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Description : If the secondary turns of a transformer are doubled and at the same time primary voltage is reduced to half then the secondary voltage will

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Answer : For measuring a very high resistance we should use Meggar.

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Description : Explain construction and working of single phase Auto transformer.

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Answer : The changes in the volume of transformer cooling oil due to the variation of atmospheric temperature during day and night is taken care of by conservator.

Description : A 1:5 step-up transformer has 120V across the primary and 600 ohms resistance across the secondary. Assuming 100% efficiency, the primary current will be:  (A) 0.2 Amp. (B) 5 Amps. (C)10 Amps. (D) 20 Amps

Answer : C. 10A

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