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

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

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

## Related questions

Description : When secondary of a current transformer is open-circuited its iron core will be?

Answer : When secondary of a current transformer is open-circuited its iron core will be hot because of heavy iron losses taking place in it due to high flux density.

Description : Define: primary and secondary distribution system

Answer : i) Primary Distribution:  It is a 3-phase, 3-wire transmission line connected in between receiving substation to Distribution substation. OR It is link between receiving substation & ... substation to consumer line. OR It is link between distribution transformer substation & consumer.

Description : Compare primary and secondary instruments.

Answer : Primary instruments  Secondary instruments  Gives magnitude of quantity in terms of physical constants of instrument  Gives reading directly of the quantity measured.  Need no calibration  ... .  e.g. magnetic meter, induction meter, hotwire meter and electrostatic meter

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

Description : A certain transformer has 200 turns in the primary winding, 50 turns in the secondary winding and 120 volts applied to the primary. What is the voltage across the secondary?  (A) 30 Volts (B) 480 Volts (C) 120 Volts (D) 60 Volts

Answer : A certain transformer has 200 turns in the primary winding, 50 turns in the secondary winding and 120 volts applied to the primary. What is the voltage across the secondary?  (A) 30 Volts (B) 480 Volts (C) 120 Volts (D) 60 Volts

Description : The secondary of a current transformer is always short-circuited under operating conditions because it?

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

Description : Write difference between absolute & secondary instrument.

Answer : Absolute Instrument Secondary Instrument 1. These give magnitude of quantity in terms physical constants of instruments 1. These give reading directly of the quantity at the time of ... Raleigh current balance. 6. Examples - ammeter, voltmeter, amperehour meter, wattmeter etc.

Description : Increasing the number of turns of wire on the secondary of a transformer will  (A) Decrease the secondary current (B) Increase the primary current (C) Have no effect on the secondary current (D) Increase the secondary current

Answer : Increasing the number of turns of wire on the secondary of a transformer will Decrease the secondary current

Description : A single phase transformer has resistance and reactance of 0.2 pu and 0.6 pu respectively. Its pu voltage regulation at 0.8 pf lagging would he

Answer : A single phase transformer has resistance and reactance of 0.2 pu and 0.6 pu respectively. Its pu voltage regulation at 0.8 pf lagging would he 0.52

Description : If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded transformer, then  (A) zero sequence currents are present on both sides of the transformer  (B) ... side  (D) zero sequence currents are present on the primary side but not on the secondary side

Answer : If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded transformer, then zero sequence currents are absent on both sides of the transformer

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

Answer : An ideal transformer has infinite values of primary and secondary inductances. The statement is false.

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

Answer : 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

Description : Primary and Backup Protection

Answer : Primary and Backup Protection  B,D,G,I are the primary protection. A,C,H,J are the backup protection. About 90% of faults are clear by Primary Protection. So ... ordinated backup (primary is at various station  and backup is at control room with computer)

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

Description : The path of magnetic flux in a transformer should have?

Answer : The path of magnetic flux in a transformer should have low reluctance.

Description : For a pulse transformer, the material used for its core and the possible turn ration from primary to secondary are respectively   (A) ferrite : 20 : 1 (B) laminated iron : 1 :1 (C) ferrite : 1 : 1 (D) powered iron : 1: 1

Answer : For a pulse transformer, the material used for its core and the possible turn ration from primary to secondary are respectively ferrite : 1 : 1

Description : Write example of each type (i) Primary transducer (ii) Active transducer (iii) Electrical transducer (iv) Digital transducer

Answer : (i) Active transducer:-Thermocouple, piezoelectric, photovoltaic cell (ii) Primary transducer:- Bourdon tube, bellows, (iii) Electrical transducer.:- LVDT,RVDT, Hall effect, strain gauge, ... , optical pyrometer, radiation pyrometer (iv) Digital transducer:- Linear Encoder, digital taco generator

Answer : The primary reason for low power factor is supply system is due to installation of induction motors.

Description : What is the definition of a primary instrument?

Description : State the meaning of absolute instrument and secondary instrument.

Answer : Absolute instruments:   These instruments read the quantity under measurement indirectly i.e. in terms of deflection, degrees and meter constant. The actual value under measurement can be calculated ... of operation (b) Depending upon permissible percentage error. (c) Depending upon application.

Description : State the losses in secondary distribution system.

Answer : The losses in secondary distribution system: a) Technical losses: 1. Due to poor voltage 2. Due to unbalance load 3. Due poor quality of transformer & its components 4. Due to poor quality ... of induction type of energy meter. 3. Lack of administration. 4. Energy theft 5. Unmetered supply

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

Answer : Secondary instruments: - Gives reading directly of the quantity being measured. - Calibrated with respect to absolute instruments  Classification of Secondary instruments:  1. Depending on the ... on permissible error: i) Standard meters ii) Substandard meters iii) First grade instruments.

Description : Why CT is never operated with an open secondary ?

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

Description : What do you mean by secondary instruments?

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

Answer : When a given transformer is run at its rated voltage but reduced frequency, its core flux density is increased.

Description : The maximum load that a power transformer can carry is limited by its?

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

Answer : When measuring insulation resistance of cables using d.c. source, the galvanometer used should be initially short circuited because Cables have a high value of capacitance which draws a high value of charging current

Description : For maximum transfer of power, internal resistance of the source should be?

Answer : For maximum transfer of power, internal resistance of the source should be equal to load resistance.

Description : What should be the ideal resistance of ammeter ?

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

Answer : The main reason for generation of harmonics in a transformer could be saturation of core.

Answer : Greater the secondary leakage flux less will be the secondary induced e.m.f.

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

Answer : A transformer oil must be free from moisture.

Answer : The full-load copper loss of a trans¬former is 1600 W. At half-load, the copper loss will be 400 W.

Answer : Iron loss of a transformer can be measured by low power factor wattmeter.

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

Answer : The dielectric strength of transformer oil is expected to be 33 kV.

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

Answer : 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 not change

Description : In a transformer the energy is conveyed from primary to secondary?

Answer : In a transformer, the energy is conveyed from primary to secondary by the flux.

Description : 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.

Answer : 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 3.0 V.

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

Description : Reduction in core losses and increase in permeability are obtained with transformer employing?

Answer : Reduction in core losses and increase in permeability are obtained with transformer employing core built-up of laminations of cold rolled grain oriented steel.

Description : A 230 V/460 V single-phase transformer operating at 20 A and unity power factor has primary referred resistance of 0.2 Ω and reactance of 0.5 Ω. The approximate primary induced emf is (A) 216 V (B) 226 V (C) 234 V (D) 236 V

Answer : A 230 V/460 V single-phase transformer operating at 20 A and unity power factor has primary referred resistance of 0.2 Ω and reactance of 0.5 Ω. The approximate primary induced emf is 226 V

Description : State and justify which of the following two transformers is better:  Transformer A = 4% voltage regulation  Transformer B = 6% voltage regulation

Answer : Transformer A with 4% voltage regulation is better.  Justification: Voltage regulation refers to the percentage change in secondary voltage when load is changed from no-load to full-load with primary voltage ... 4% voltage regulation, which is less as compared to 6% of transformer B, it is better.

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

Answer : Construction of single phase auto transformer: (i) It has only one winding wound on a laminated circular magnetic core. (ii) The core is made of silicon steel stampings. (iii) The two terminals of the ... help of handle. 5) The same transformer can be used as step-up or step down auto-transformer

Description : 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 which part of the transformer?

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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