The electrical current from the battery of your car is too weak to provide direct power for the automobile lights. It is far too weak to provide power for the ignition system, much so, to sustain it. However, the electrical power that is used during start ignition is derived from the car battery. It is the same electricity that allows the spark plugs to discharge high-voltage electrical sparks. This is made possible by the ignition coil. It is the built-in transformer of your automobile. It is a step-up transformer that multiplies the weak voltage from the batteries before being distributed to the rest of the ignition system.
As a step-up transformer, the ignition coil increases the electrical power output at least one-thousand fold. It achieves this through the process known as electromagnetic induction. It is a process whereby an electromagnet or a permanent magnet induces the production of voltage. An ignition coil is comprised of two sets of coils, namely, the input coils and the output coil. These coils are wound around a multi-layered toroid iron core. The input coil has greater number of windings compared to the output coil. This makes the input coil produce a stronger magnetic field that is transmitted by the toroid core.
The electromagnetic field of the input coil induces high-voltage current to the output coil. In turn, the output coil sends high-voltage current to the other components of the ignition system. Every time the ignition key is turned, low voltage current flows from the car battery to the ignition coil. The ignition coil is responsible for multiplying the weak voltage of the battery. In so doing, the starter motor and spark plugs will have enough power to start and sustain fuel combustion. When fuel combustion is already sustainable, the burden of supplying electricity shifts from the battery to the alternator.
