68.
(a) The flux in coil 1 is
L
1
i
1
N
1
=
(25 mH)(6.0 mA)
100
= 1.5 µWb ,
and the magnitude ofthe self-induced emfis
L
1
di
1
dt
= (25 mH)(4.0 A/s) = 100 mV .
(b) In coil 2, we find
Φ
21
=
M i
1
N
2
=
(3.0 mH)(6.0 mA)
200
= 90 nWb ,
E
21
= M
di
1
dt
= (3.0 mH)(4.0 A/s) = 12 mV .