A long solenoid is made by closely winding turns of wire of diameter d (together with insulation) (Fig. 27.5). The wire carries a current i. Find the magnetic field induction in the centre O and on the end A of the solenoid. out the calculation for d =0.1 mm, i =5 A.

Answer

`6.3 xx 10^(-2)T; 3.1 xx 10^(-2)T`

Explanation

The induction of the magnetic field in the centre of a long solenoid is `B=mu_(0) "in"=mu_(0)iw//l`. If the wire is closely wound (see Fig. 27.5), the diameter of the insulated wire is d= l/w. Hence `B=mu_(0)i//d`. At the end of the solenoid the field is twice as weak.