Final answer:
An ignition coil in an automobile is a step-up transformer, increasing voltage while decreasing current to create a high-voltage spark. Transformers have high efficiency, usually above 99%, ensuring minimal loss of power in the transformation process.
Step-by-step explanation:
An ignition coil in an automobile is an example of a step-up transformer. A step-up transformer works by increasing voltage while decreasing current, which is essential for creating the high-voltage spark needed in spark plugs to ignite the fuel-air mixture in an engine. By contrast, a step-down transformer decreases voltage and increases current. Transformers obey the principle of conservation of power as shown by the equation Pp=IpVp=IsVs=Ps, where Ip and Is represent the currents in the primary and secondary coils respectively, and Vp and Vs represent the voltages.
Regarding efficiency, transformers are generally very effective, with efficiency rates often exceeding 99%. This means that the electrical power output nearly equals the power input when resistance is negligible. This efficiency is key in various applications, such as the ignition coil in vehicles, which must reliably convert a lower input voltage to a much higher output voltage.