5. Two questions:
Refer to the diagram below, which is a highly simplified layout of the ignition circuit for a car.
Ignore first the alternator and voltage regulator. The "heart" of the ignition system is the ignition coil. This coil is really a mutual inductor/transformer with a "primary" coil consisting of, say, 100 turns of medium-sized wire, and a "secondary" coil of thousands of turns of finer wire. The battery is connected to the primary of the ignition coil through the "points". On older cars, the points is simply a mechanical switch that opens and shuts by a rotary drive taken off the engine; modern ignition cars use electronic switches, but the idea is the same. Thus, the current flowing through the primary coil is switched on and off. When the points close, the current in the circuit rapidly increases; this, in turn, leads to an induced emf in the secondary coil. Note, because the induced emf in the secondary is given by e = M(di/dt), it is the rate of change of current (di/dt) in the primary that produces the change in flux and, hence, the emf, in the secondary coil. In fact, the induced emf may be many thousands of times greater than the 12V produced by the car battery, and approaching, say, 50,000V! This emf pulse is directed by the distributor to the spark-plugs via the spark-leads, where it produces a spark that ignites the gas/air mixture in the cylinder.
Clearly, the "timing" of this sequence of events is important, which is why the distributor and the points have to be carefully adjusted to be in the proper synchronization not only with each other but the position of the piston in the cylinder. The distributor directs the secondary emf pulses to each of the spark-plugs in turn. So called "high performance coils" have a higher mutual inductance M than regular coils. Although you might think that's a good thing, you should bear in mind that a coil with a higher inductance produces a greater emf pulse and in turn that requires a secondary circuit that can carry the higher currents.
Now to the second part of the question ... the alternator/voltage regulator system is simply a voltage generator that is driven by belts off the engine. So, as the engine rotates, the coils in the alternator rotate and produce an emf. That emf is regulated so that it is roughly constant, i.e., independent of angular velocity (i.e., engine speed), and just greater than 12V (so the car battery is constantly being charged). If you disconnect the battery terminals, the alternator will still continue operating and so it will take the place of the battery in supplying emf to the primary coil. So, providing the engine is running, the alternator produces the emf that is used to produced the energy for the sparks, which drives the engine ... which drives the alternator, etc. This process should continue until the car runs out of gas!
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