Which device is commonly found in automobile ignition systems using mutual induction?

The ignition coil is a crucial component in automobile ignition systems that operates on the principle of mutual induction. It is responsible for converting the low voltage from the battery into the high voltage needed to create a spark at the spark plugs, igniting the engine's air-fuel mixture. The ignition coil consists of two coils of wire: a primary winding with fewer turns and a secondary winding with many more turns.

When the primary coil experiences a change in current, it creates a magnetic field that induces a high voltage in the secondary coil due to mutual induction. This high voltage is what produces the electric spark that initiates combustion in the engine's cylinders. The design and function of the ignition coil are key to ensuring efficient engine performance and reliable starting.

In contrast, while alternators and starter motors are also essential for the overall operation of an automobile's electrical system, they do not directly engage in the ignition process through mutual induction. The battery serves as the power source for the entire system but does not function on the principle of mutual induction. Therefore, the ignition coil is the correct answer as it specifically utilizes mutual induction to fulfill its role in the ignition system.