Question

A solenoid has a core of a material with relative permeability `400`. The windings of the solenoid are insulated from the core and carry a current of `2A`. If the number of turns is `1000` per metre, calculate (i) H (ii) B (iii) Intensity of magnetisation I, and the magnetising current.

Answer 1

(a) The field H is dependent of the material of the core, and is `H=nI=1000xx2.0=2xx10^(3)A//m`.
(b) The mangetic field b is given by
`B=n mu_( r)m u_(o)H`
`=400xx4pixx10^(-7)(N//A^(2))xx2xx10^(3)(A//m)`
=1.0T
(c) Mangetisation is given by
`M=(B-mu_(0)H)//mu_(0)`
`=(mu_(r)mu_(0)H-mu_(0)H)//mu_(0)=(mu_(r)-1)H=300xxH` ltbr gt `=8xx10^(5)A//m`
(d) The mangetising current `I_(M)` is the additional current that needs to be passed throught the wtndings of the solenoid in the absence of the core which would give a B value as in the presence of the core. thus `B=mu_(r)n_(0)(I+I_(M))`. using I=2A,B=1T, we get `I_(M)=794A`.