Description : 29.In transformer terminology, the ratio 20:1 indicates that A. there are 20 turns on primary one turn on secondary B. secondary voltage is 1/20th of the primary C. primary current is 20 times greater than the secondary current D. for every 0 turns on primary, there is one turn on secondary
Last Answer : A. there are 20 turns on primary one turn on secondary
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
Last 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 : 57 In a transformer the resistance between its primary and secondary is A. Zero B. 1Ω C. 1000 Ω D. Infinite
Last Answer : D. Infinite
Description : An AC supply of 230 V is applied to a half-wave rectifier circuit through a transformer having primary to secondary turn’s ratio 12:1. The peak inverse voltage is A) 8.62 V B) 12 V C) 19.17 V D) 27.11 V
Last Answer : An AC supply of 230 V is applied to a half-wave rectifier circuit through a transformer having primary to secondary turn’s ratio 12:1. The peak inverse voltage is A) 8.62 V B) 12 V C) 19.17 V D) 27.11 V
Description : In a Tap changing transformer on which side is the tap connected, primary side or secondary side?
Last Answer : A. Tapings are always connected to high voltage winding side, because of low current. If we connect tapings to low voltage side, sparks will produce while tap changing operation due to high current.
Description : What will happen if the primary of a transformer is connected to D.C. supply? (A) Transformer will operate with low efficiency (B) Transformer will operate with high efficiency (C) No effect (D) Transformer may start to smoke and burn
Last Answer : What will happen if the primary of a transformer is connected to D.C. supply? (A) Transformer will operate with low efficiency (B) Transformer will operate with high efficiency (C) No effect (D) Transformer may start to smoke and burn
Description : If we give 2334 A, 540V on Primary side of 1.125 MVA step up transformer, then what will be the Secondary Current, If Secondary Voltage=11 KV?
Last Answer : A. As we know the Voltage & current relation for transformer-V1/V2 = I2/I1 We Know, VI= 540 V; V2=11KV or 11000 V; I1= 2334 Amps. By putting these value on Relation540/11000= I2/2334 So,I2 = 114.5 Amps
Description : 66 While conducting short-circuit test on a transformer the following side is short circuited A. High voltage side B. low voltage side C. primary side D. secondary side
Last Answer : B. Low voltage side
Description : The frequency of the secondary voltage of a transformer will be..... A. less than frequency of the primary voltage B. equal to the primary voltage C. greater than the frequency of the primary voltage D. much greater than the frequency of the primary voltage
Last Answer : B. Equal to the primary voltage
Description : During short circuit test iron losses are negligible because A. The current on secondary side is negligible B. The voltage on secondary side does not vary C. The voltage applied on primary side is low D. Full-load current is not supplied to the transformer
Last Answer : C) the voltage applied on primary side is low
Description : 21.The ordinary two winding transformer's primary and secondary windings always have A. different no of turns B. same size of copper wire C. a common magnetic circuit D. separate magnetic circuits
Last Answer : C. A common magnetic circuit
Description : When the turns ratio of a transformer is 20 and the primary ac voltage is 12 V, the secondary voltage is? A.12 V B.120 V C.240 V D.2,400 V
Last Answer : When the turns ratio of a transformer is 20 and the primary ac voltage is 12 V, the secondary voltage is? A.12 V B.120 V C.240 V D.2,400 V
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
Last Answer : Increasing the number of turns of wire on the secondary of a transformer will Decrease the secondary current
Description : A load with an impedance of 440 ohms is connected across the secondary of the transformer illustrated. If the input voltage is 110 VAC and the step-up ratio is 10 to 1, what will be the primary current? EL-0055 A. 2.5 amps B. 25 amps C. 250 amps D. current cannot be determined with information given
Last Answer : Answer: B
Last Answer : The full-load copper loss of a trans¬former is 1600 W. At half-load, the copper loss will be 400 W.
Last Answer : yes High Voltage side of Transformer winding have more number of turns. and low voltage side of Transformer winding have less number of turns.
Description : A load is connected to the secondary of the transformer illustrated and the current through the load is 10 amps. If the step-up ratio is 10 to 1 and the input voltage is 110 VAC, what will be the current flow through the primary? EL-0055 A. 1 amp B. 10 amps C. 100 amps D. 1000 amps
Last Answer : Answer: C
Description : Why does a transformer only work with an AC supply?
Last Answer : The transformer work depends on the induction as main principle ,for that AC is the right means
Description : The inrush current of a transformer at no load is maximum if the supply voltage is switched on (1) at peak voltage value (2) at zero voltage value (3) at half voltage value (4) at 0.866 time voltage value
Last Answer : At 0.866 time voltage value
Description : A certain transformer has 400 turns in the primary winding and 2,000 turns in the secondary winding. The turns ratio is? A.0.2 B.0.4 C.5 D.25
Last Answer : A certain transformer has 400 turns in the primary winding and 2,000 turns in the secondary winding. The turns ratio is? A.0.2 B.0.4 C.5 D.25
Description : What current flows in the transformer primary when its secondary is open?
Last Answer : A. When the secondary is open, there is no current in the secondary of the transformer. The primary takes a small current I0) from the source called no-load current which has a magnetizing ... ) producing the magnetic flux and a working component (I0 cosθ0) supplying real power for iron losses.
Description : 59.An ideal transformer has infinite values of primary and secondary inductances. The statement is A. True B. False
Last Answer : B. False
Description : 50 The equivalent resistance of the primary of the transformer having K = 5, R1 = 0.1 ohm when referred to secondary becomes .....ohm A. 0.5 B. 0.02 C. 0.004 D. 2.5
Last Answer : A. 0.5
Description : 38] In a transformer the energy is conveyed from primary to secondary? A. Through cooling coil B. Through air C. By the flux D. None of the above
Last Answer : C. By the flux
Description : 28.In a two winding transformer, the emf /turn in secondary winding is always......the induced emf power turn in primary A. equal to k times B. equal to 1/k times C. equal D. greater than
Last Answer : C. equal
Description : 6 In a two winding transformer, the primary and secondary induced emf E1 & E2 are always A. equal in magnitude B. anti phase with each other C. in phase with each other D. determined by load on transformer secondary
Last Answer : C. In phase with each other
Description : 12] Which is not the basic element of the transformer? A. core B. primary winding C. secondary winding D. mutual flux
Last Answer : D. Mutual flux
Last Answer : An ideal transformer has infinite values of primary and secondary inductances. The statement is false.
Description : In a transformer the resistance between its primary and secondary should be?
Last Answer : In a transformer the resistance between its primary and secondary should be infinity.
Description : What will happen if DC supply is given on the primary of a transformer?
Last Answer : A. Mainly transformer has high inductance and low resistance. In case of DC supply there is no inductance, only resistance will act in the electrical circuit. So, high electrical current will flow through primary side of the transformer. Due to this the coil and insulation will burn out.
Last Answer : A transformer cannot raise or lower the voltage of a D.C. supply because Faraday's laws of electromagnetic induction are not valid since the rate of change of flux is zero.
Description : An AC supply of 230 V is applied to half wave rectifier circuit. A transformer turns ratio is 20 : 1. Find i) Output DC voltage (ii) Peak Inverse Voltage (PIV)
Last Answer : Solution:
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
Last 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
Last Answer : High voltage winding in a transformer has more number of turns.
Last Answer : In a power or distribution transformer about 10 percent end turns are heavily insulated to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns.
Description : A load with an impedance of 440 ohms is connected across the secondary of the device illustrated. If the input voltage is 110 VAC and the step-up ratio is 10 to 1, what will be the primary current? EL-0055 A. 2.5 amps B. 25 amps C. 250 amps D. current cannot be determined with information given
Description : A 40 kVA transformer has a core loss of 400 W and a full load copper loss of 800 W. The proportion of full load at maximum efficiency is
Last Answer : A 40 kVA transformer has a core loss of 400 W and a full load copper loss of 800 W. The proportion of full load at maximum efficiency is 0.707
Description : The primary coil of a transformer is connected to a 60 V ac source. The secondary coil is connected to a 330 ohms load. The turns ratio is 3:1. What is the secondary voltage? A.2 V B.20 V C.180 V D.18 V
Last Answer : The primary coil of a transformer is connected to a 60 V ac source. The secondary coil is connected to a 330 ohms load. The turns ratio is 3:1. What is the secondary voltage? A.2 V B.20 V C.180 V D.18 V
Description : Normal values of overflow rate for sedimentation tanks using coagulants in litres/hr/m2 , generally range between (A) 250 to 500 (B) 500 to 750 (C) 750 to 1000 (D) 1000 to 1250
Last Answer : (D) 1000 to 1250
Description : Normal values of overflow rate for plain sedimentation tank, is (A) 250 to 500 litres/hr/m2 (B) 500 to 750 litres/hr/m2 (C) 750 to 1000 litres/hr/m2 (D) 1000 to 1250 litres/hr/m
Last Answer : (B) 500 to 750 litres/hr/m
Description : Turn ratio of a transformer is 5. If 220 V AC is applied to its primary coil, voltage in the secondary coil will be: a. 44V b. 4.4 V c. 220V d. 1100V
Last Answer : c. 220V
Description : Can transformer convert AC to DC?
Last Answer : No, Transformer cannot convert AC to DC.
Description : Does the transformer draw any current when its secondary is open?
Last Answer : Yes, no-load primary current.
Description : Does the transformer draw any current when secondary is open ? Why ?
Last Answer : Yes,it (primary) will draw the current from the main supply in order to magnetize the core and to supply iron and copper losses on no load . There will not be any current in the secondary since secondary is open
Description : 48.During light loads, the transformer efficiency is low because A. Secondary output is low B. Transformer losses are high C. Fixed loss is high in proportion to the output D. Cu loss is small
Last Answer : C. Fixed loss is high in proportion to the output
Description : When secondary of a current transformer is open-circuited its iron core will be?
Last 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 : The secondary of a current transformer is always short-circuited under operating conditions because it?
Last Answer : The secondary of a current transformer is always short-circuited under operating conditions because it avoids core saturation and high voltage induction.
Description : If the illustrated device has a step-up ratio of 10 to 1 what voltage be measured at the secondary shortly after the primary of the device is connected to 110 volts DC with a current of 12 amps? EL-0055 A. 0 volts B. 110 volts C. 1000 volts D. 1100 volts
Last Answer : Answer: A
Description : A load is connected to the secondary of the device illustrated and the current through the load is 10 amps. If the step-up ratio is 10 to 1 and the input voltage is 110 VAC, what will be the current flow through the primary? EL-0055 A. 1 amp B. 10 amps C. 100 amps D. 1000 amps