Ans. Where the pole pieces are simply extensions of the cores without enlargement, the coils can be slipped over the ends, but some kind of clamping device is necessary to hold them in place, as for instance, the method shown in fig. 244. In case the pole piece be made larger than the core and separate therefrom, it is put into position after the coils are in place, thus serving the double purpose of pole piece and clamp. =Ques. Describe the coil connections.= Ans. Coils are generally united in series so that the same magnetizing current may flow through all of them. The coils should be so connected that they produce alternate north and south poles. If all the coils be similarly wound with respect to the terminals, and similarly placed; that is, so placed that the winding, considered from the coil terminal nearest the pole face, starts in all the coils in the same direction, then the connections will come at the north end and at the south end of the spools. [Illustration: FIG. 245.--Western Electric set of former wound field coils for four pole dynamo. These coils are wound around a former or template, and are then slipped over the cores before the latter are bolted to the yokes or frame.] =Heating.=--The heat generated in the magnetizing coils is dissipated in three ways; by: 1. Induction; 2. Radiation; 3. Convection. In the first instance, it passes through the copper and the insulation, either to the external surface, whence it passes off by radiation and convection into the air, or to the magnet core and yoke, which in turn conduct it away. In large multi-polar machines the masses of metal in the pole cores and frame are more efficient in dissipating heat than the external surface of the coil. [Illustration: FIG. 246.--Fort Wayne compound wound rectangular ventilated spool field coil. The series and shunt coils are wound side by side, ventilating passages being provided lengthwise through each coil and between the shunt and series coils as shown.] =Ventilation.=--Sometimes provision is made for ventilation of the field magnet coils as shown in fig. 246. Here the series and shunt coils are wound side by side, ample ventilation being provided lengthwise through and between the coils. HAWKINS PRACTICAL LIBRARY OF ELECTRICITY IN HANDY POCKET FORM PRICE $1 EACH _They are not only the best, but the cheapest work published on Electricity. Each number being complete in itself. Separate numbers sent postpaid to any address on receipt of price. They are guaranteed in every way or your money will be returned. Complete catalog of series will be mailed free on request._ =ELECTRICAL GUIDE, NO. 1= Containing the principles of Elementary Electricity, Magnetism, Induction, Experiments, Dynamos, Electric Machinery. =ELECTRICAL GUIDE, NO. 2=