elements or devices interposed so that the current must pass through these before it will complete its circuit. Q. What is the difference between a closed and open circuit? A. A closed circuit is one that provides an unbroken or continuous path fo the transmission of electrical energy while an open circuit is one in which there is a gap or resistance sufficiently great to prevent the electrical energy from passing between the various members comprising the circuit. Electricity can flow only over a closed circuit, except in cases where the pressure of the current is great enough so that it may overcome or bridge the gap or resistance in an open circuit. Q. How many circuits are there in the usual ignition system? A. There are two circuits in the conventional high tension ignition systems, these being the primary and secondary circuits. respectively. primary circuit? A. The primary circuit includes the source of current or battery, the switch, the ignition timer and the primary winding of the transformer or induction coil. (See Figs. 77A and 78.) Fig. 77A.-Simple High Tension Ignition System for One Cylinder Motor Showing Arrangement and Wiring of Principal Parts. Q. What parts are in the secondary circuit? A. The secondary circuit includes the high tension winding of the induction coil and the spark plug. Q. Describe parts of simple battery ignition system. A. A simple battery ignition system for a single cylinder engine is shown at Fig. 77A and a corresponding system for a two cylinder engine is outlined at Fig. 78. The current supply is obtained from two sets of cells, one of these being a dry battery, the other a storage Fig. 78.-High Tension Ignition System for Two-Cylinder Opposed Motor. battery. One wire from the negative or minus terminal (-) of each battery leads to a button on the switch. The plus terminal (+) or positive, as it is commonly termed, of each battery is grounded to the engine frame. A single wire leads from the top of the switch to one of the primary terminals of the induction coil. The other primary terminal of the induction coil is connected to the insulated terminal on the contact maker or timer. A heavily insulated wire joins the secondary terminal of the induction coil with the insulated terminal of the spark plug. The action of this method of ignition may be easily understood |