Page:Motors and motor-driving (1902).djvu/190

158 the plate will pass beneath the spring, thereby completing the electrical circuit from the battery through , and on to the metal of the motor, whence it returns to the coil. To effect the rapid interruption of the current a trembler is provided on the coil. The action of this is as follows:—

When a current is allowed to flow round the thick or primary winding of the coil, the iron wires, which it will be remembered composed the core, become magnetised, and attract the iron knob of the spring armature. The current for this purpose is led through the screw to a platinum point



on. The moment this occurs the contact-piece on leaves the point of the screw, with the result that  instantly loses its power of attraction; this action is repeated with great rapidity so long as the circuit is completed by  and. The screw's requires to be adjusted in just the same manner as in the De Dion system, though it must be remembered that the action is reversed, the trembler being in contact with it so long as  and  are apart. In engines provided with two or more cylinders an easy method of testing the spark in each cylinders becomes apparent. In most systems a separate coil is required for each cylinder. Having put the engine in motion,