A step-up transformer is used on a 120 V line to provide a potential difference of 2400 V. If the primary coil has 75 turns, the number of turns in the secondary coil is
150
1200
1500
1575
A low-loss transformer has 230 V applied to the primary and gives 4.6 V in the secondary. Secondary is connected to a load which draws 5 A of current. The current in the primary is
0.1 A
1 A
10 A
250 A
The primary winding of a transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an a.c. supply of 20 V, 50 Hz. The secondary will have an output of
2 V, 50 Hz
200 V, 50 Hz
200 V, 500 Hz
2 V, 5 Hz
The best material for the core of a transformer is
stainless steel
soft iron
hard steel
mild steel
In a noiseless transformer, an alternating current of 2 A is flowing in the primary. The number of turns in the primary and secondary coils are 100 and 20 respectively. The value of current in the secondary is
0.08 A
0.4 A
5 A
The magnetic effect of current was discovered by
Maxwell
Fleming
Oersted
Faraday
Given below are two statements, one labelled as Assertion (A) and the other labelled as Reason (R)
Assertion (A) : Transformer is useful for stepping up or stepping down voltages.
Reason (R) : Transformer is a device used in D.C. circuits.
In the context of the above two statements, which one of the following is correct?
Both A and R are true and R is the correct explanation of A
Both A and R are true but R is not a correct explanation of A
A is true but R is false
A is false but R is true
Iron core is used in a transformer to
provide tight magnetic coupling
increase the weight
reduce copper losses
increase copper losses
Hot wire ammeters are used for measuring
a.c.only
d.c. only
both a.c and d.c
none of these
A step-up transformer operates on 230 V line and supplies a load of 2 A. The ratio of primary and secondary turns is 1 : 25. The current in the primary is
50 A
25 A
15 A
12.5 A
