4)
As
a parallel-plate capacitor with circular plates 1 cm in diameter is
being
charged, the current density of the displacement current in the region
between
the plates is uniform and has a magnitude of 176 A/m2.
[
N.B. Wherever π appears in your answers
simply
leave it as π
]
(a)
What
is the total displacement current between the plates ?
(5)
For uniform J, id = JA = 176 x π x 10-4 x 0.25 = 44π x 10-4 A
(b)
Calculate
the magnitude, B of the magnetic field at a distance r = 2.5 mm from
the axis
of symmetry of this region.
(15)
[
µ0 = 4p x 10-7 N/A2
]
Ampere's
Law 
C is a cicular loop, radius r
centered on the axis of the capacitor. The plane of the loop is
parallel to the pates of the capacitor. By symmetry the B field
is constant in magnitude on this loop such that,
(c)
Calculate
dE/dt in this region.
(5)
[
Use ε0 = 8.8 x 10-12
F/m ]
