YASH CLASSES
2 MAGNETIC EFFECTS OF ELECTRIC CURRENT [ X ]
10. Which
one of true :
(a) soft
iron is less
strongly magnetized by
induction than steel
.
(b) soft
iron is more
strongly magnetized by
induction
than steel .
(c) soft
iron loses its magnetism
to a lesser
extent
than steel .
11. The
back emf of
an electric motor
is
greatest
when the motor is :
(a) first switch
(b) speeding
(c) at
maximum (d) slowing
up
12. In India A.C. voltage and frequency used
are
respectively :
(a)
220V , 60 Hz (b) 220V , 50 Hz
(c) 420V
, 60 Hz (d)
110V , 60 Hz
13. Magnetic
field lines determine
strength :
(a)
only the direction
of the field
(b)
the relative strength
of the field
(c)
both direction and
strength
(d)
only the shape
of the field
14. When live wire and neutral
wire contact
(a) short – circuit occurs
(b)
circuit current increase
enormously
(c) circuit
current decrease to a small value
(d)
all of the
above .
15. A magnet
attracts small pieces
of
(a) iron
(b)
cobalt (c) nickel
(d) all above
16. magnetic
field produced by a
current in
straight wire
has poles
(a) north
(b) south (c)
both (d) non