(b) How does this magnetic energy compare with the
electrostatic energy stored in a capacitor Solution
(a)
From Eq (6 17), the magnetic energy is
2
21
UB
LI
=
=




=
(
)
1
2
2
L
B
n
nI
µ
µ
0
0
sinceB
 
for a solenoid
,
 EXAMPLE 6