The magnetic effect of current was discovered by
Maxwell
Fleming
Oersted
Faraday
Which quantity is increased in a step-down transformer?
voltage
frequency
power
current
Hot wire ammeters are used for measuring
a.c.only
d.c. only
both a.c and d.c
none of these
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 and secondary of a transformer are
electrically coupled
capacitively coupled
magnetically coupled
A transformer is an efficient device because it
uses inductive coupling
is a static device
uses electric coupling
uses capacitive coupling
A transformer will work on
a.c. only
a.c. as well as d.c.
none of the above
A transformer is used to reduce the mains supply of 220 V to 11 V. If currents in the primary and secondary are 5 A and 90 A respectively, efficiency of the transformer is
75%
60%
40%
90%
A transformer of 100% efficiency has 500 turns in the primary and 10,000 turns in the secondary. If the primary is connected to 220 V mains supply, what is the voltage across the secondary?
2500 V
4000 V
3500 V
4400 V
The unit of self inductance is
henry
weber/m2
siemens
ampere-turn per weber
