Saturday, 14 February 2015

Transformer multiple choice questions part 1

Hello Engineer's

Q.[1] A transformer transforms

(a) frequency
(b) voltage
(c) current
(d) voltage and current
Ans : D

Q.[2] Which of the following is not a basic element of a transformer ?

(a) core
(b) primary winding
(c) secondary winding
(d) mutual flux.
Ans : D

Q.[3] In an ideal transformer,

(a) windings have no resistance
(b) core has no losses
(c) core has infinite permeability
(d) all of the above.
Ans : D

Q.[4] The main purpose of using core in a transformer is to

(a) decrease iron losses
(b) prevent eddy current loss
(c) eliminate magnetic hysteresis
(d) decrease reluctance of the common magnetic circuit.
Ans :D

Q.[5] Transformer cores are laminated in order to

(a) simplify its construction
(b) minimize eddy current loss
(c) reduce cost
(d) reduce hysteresis loss.
Ans : B

Q.[6] A transformer having 1000 primary turns is connected to a 250-V a.c. supply. For a secondary voltage of 400 V, the number of secondary turns should be

(a) 1600
(b) 250
(c) 400
(d) 1250
Ans : A

Q.[7] The primary and secondary induced e.m.fs. E1 and E2 in a two-winding transformer 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.
Ans : C

Q.[8] A step-up transformer increases

(a) voltage
(b) current
(c) power
(d) frequency.
Ans : A

Q.[9] The primary and secondary windings of an ordinary 2-winding transformer always have

(a) different number of turns
(b) same size of copper wire
(c) a common magnetic circuit
(d) separate magnetic circuits.

Ans : C

Q.[10] In a transformer, the leakage flux of each winding is proportional to the current in that winding because

(a) Ohm’s law applies to magnetic circuits
(b) leakage paths do not saturate
(c) the two windings are electrically isolated
(d) mutual flux is confined to the core.

Ans : B

Q.[11] In a two-winding transformer, the e.m.f. per turn in secondary winding is always .......the induced e.m.f. power turn in primary.

(a) equal to K times
(b) equal to 1/K times
(c) equal to
(d) greater than.
Ans : C

Q.[12] In relation to a transformer, the ratio 20 : 1 indicates that

(a) there are 20 turns on primary one turn on secondary
(b) secondary voltage is 1/20th of primary voltage
(c) primary current is 20 times greater than the secondary current.
(d) for every 20 turns on primary, there is one turn on secondary.
Ans : D

Q.[13] In performing the short circuit test of a transformer

(a) high voltage side is usually short circuited
(b) low voltage side is usually short circuited
(c) any side is short circuited with preference
(d) none of the above.
Ans : B

Q.[14] The equivalent resistance of the primary of a transformer having K= 5 and R1= 0.1 ohm when referred to secondary becomes.......ohm.

(a) 0.5
(b)0.02
(c) 0.004
(d) 2.5
Ans : D

Q.[15] A transformer has negative voltage regulation when its load power factor is

(a) zero
(b) unity
(c) leading
(d) lagging
Ans : C

If you have any doubt then comment below.


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