200
CHAPTER 20
(a) From the above result, note that the induced current has greatest magnitude when
B
∆∆
t
is the greatest (that is, when the graph of
B
vs.
t
has the steepest slope).
From Figure (a) above, this is seen to be in the interval
between
0 and
2.0 s
tt
==
.
(b)
0 when
0
B
=∆
∆
I
(that is, when
B
is constant). This is true in the interval
t
=
between
2.0 s and
4.0 s
.
(c) No. The direction of the induced current will always be such as to oppose the
change that is occurring in the flux through the coil. When
B
is decreasing the
change in the flux (and hence the induced current) is directed opposite to what it is
when
B
is increasing.
(d) Between
t
, the flux through the coil is directed into the page and
decreasing
in magnitude. The induced current must flow
0 and
2.0 s
t
clockwise around the coil
so that the flux it generates through the interior of the coil is into the page opposing

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