A coil is wound on an iron core and looped back on itself so that the core has two sets of closely wound wires in series carrying current in the opposite senses. What do you expect about its self-inductance? Will it be large or small?

A closely wound coil of 100 turns and area of cross-section 1cm^(3) has a coefficient of self-induction 1 mH. The magnetic induction in the centre of the core of the coil when a current of 2A flows in it, will be

A long solenoid of length 1 m, cross sectional area 10 cm^2 , having 1000 turns has wound about its centre a small coil of 20 turns. Compute the mutual inductance of the two circuits. What is e.m.f. in the coil when the current in the solenoid chanages at the rate of 10 As^-1 ?

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 m^2 . 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.