If you have the following circuit with a step up voltage from L1 to L2, then when do you get a spark across the spark plug? I have three scenarios.
Scenario 1. You have the switch open, then you close it right away you get a spark.
Scenario 2. You have the switch open, then you close the switch. This allows the magnetic lines of flux to expand. A current then is induced for L2. Once a little time passes you reopen the switch, and then you get a spark.
Scenario 3. Neither of these, I am dead wrong.
simulate this circuit – Schematic created using CircuitLab
Best Answer
Scenario #2 is the correct one.
Without some type of voltage step up a 12V battery can not create a high enough change in current to create a spark. If instead current is set up through the coil and then the path is broken the change in current is orders of magnitude higher.
To make this circuit practical the addition of a capacitor across the switch is needed to make the switch break clean. This would work like a condenser in a point and breaker automotive ignition.