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
Hot wire ammeters are used for measuring
a.c.only
d.c. only
both a.c and d.c
none of these
Iron core is used in a transformer to
provide tight magnetic coupling
increase the weight
reduce copper losses
increase copper losses
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
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 transformer, the number of turns of primary coil and secondary coil are 5 and 4 respectively. If 240 V is applied on the primary, then the ratio of currents in the primary and secondary coil is
4 : 5
5 : 4
1 : 3
3 : 1
The unit of self inductance is
henry
weber/m2
siemens
ampere-turn per weber
The primary and secondary of a transformer are
electrically coupled
capacitively coupled
magnetically coupled
Which quantity is increased in a step-down transformer?
voltage
frequency
power
current
