0 = 2 ×103 A/m (b) The magnetic field B is given by
B = mr m0 H
   = 400 × 4p ×10–7 (N/A2) × 2 × 103 (A/m)
   = 1 0 T
(c) Magnetisation is given by
M = (B– m0 H)/ m0
    = (mr m0 H–m0 H)/m0 = (mr – 1)H = 399 × H
     @ 8 × 105 A/m
(d) The magnetising current IM is the additional current that needs to
be passed through the windings of the solenoid in the absence of
the core which would give a B value as in the presence of the core Thus B = mr n (I + IM)