Turns, Primary Ampere-

The ampere-turns in a primary circuit of an induction coil or transformer. In an electric welding transformer, or in the transformer used in the alternating current system, where efficiency is an important element, the ampere-turns in primary and secondary for an efficiency of 100 per cent. should be equal. In the case of an experimental induction coil other considerations outweigh that of mere efficiency. Insulation, including security from piercing, and the production of as long a spark as po ible, are, in these cases, the controlling consideration. [Transcriber's note: A 100 per cent efficient transformer is impo ible, but over 99 per cent is common. At room temperature there is always some lost flux, eddy currents and resistive lo es.]