Question

A magnetic field of 100 G (1 G = 10⁻⁴ T) is required which is uniform in a region of linear dimension about 10 cm and area of cross-section about 10⁻³ m². The maximum current carrying capacity of a given coil of wire is 15 A and the number of turns per unit length that can be wound round a core is at most 1000 turns m⁻¹. Suggest some appropriate design particulars of a solenoid for the required purpose. Assume the core is not ferromagnetic

Answer 1

Magnetic field strength, B = 100 G = 100 × 10⁻⁴ T
Number of turns per unit length, n = 1000 turns m⁻¹

Current flowing in the coil, I = 15 A
Permeability of free space, 0 = 4π × 10^–7 T m A^–1
Magnetic field is given by the relation,

If the length of the coil is taken as 50 cm, radius 4 cm, number of turns 400, and current 10 A, then these values are not unique for the given purpose. There is always a possibility of some adjustments with limits.