Alternating Current

Chokes are inductances that isolate AC frequency current from certain areas of a radio circuit. Chokes depend upon the property of self-inductance for their operation. They are used to block alternating current while passing direct current. Radio frequency coil ie, a low frequency choke coil is made of insulated copper wire wound on a soft iron core.

Soft iron is used for making transformer cores. In these cases the material goes through complete cycles of magnetisation continuously. The material must therefore have a low hysteresis loss to have less dissipation of energy and hence a small heating of the material (otherwise the insulation of the windings may break), a high permeability (to obtain a large flux density at low field) and a high specific resistance (to reduce eddy current loses). These requirements are fulfilled by soft iron. Hence compared to steel iron and alnico soft iron is preferred for use as core of a transformer.

Power factor This gives, when is doubled, we find =