The best material for the core of a transformer is
stainless steel
soft iron
hard steel
mild steel
The unit of self inductance is
henry
weber/m2
siemens
ampere-turn per weber
A transformer is having 2100 turns in the primary and 4200 turns in the secondary. An a.c. source 120 V, 10 A is connected to the primary. The secondary voltage and current are :
120 V, 10 A
240 V, 10 A
120 V, 20 A
240 V, 5 A
The magnetic effect of current was discovered by
Maxwell
Fleming
Oersted
Faraday
In a step-down transformer, the e.m.f. induced per turn
is more in primary
is less in primary
same in primary and secondary
none of the above
Iron core is used in a transformer to
provide tight magnetic coupling
increase the weight
reduce copper losses
increase copper losses
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
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
10 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
Quantity that remains unchanged in a transformer is
voltage
current
frequency
none of these
