What is the main purpose of a transformer?

The main purpose of a transformer is to change the voltage level of alternating current (AC). Transformers are electrical devices that work specifically with AC, allowing for the adjustment of voltage levels to suit different applications and transmission needs. By using electromagnetic induction, transformers can either step up (increase) or step down (decrease) the voltage while maintaining the overall power level (with some losses due to efficiency).

This functionality is crucial in power distribution systems, where electricity generated at high voltages is transformed to lower voltages for safe use in residential and commercial applications. Additionally, transformers help minimize energy loss during transmission over long distances by allowing electricity to be sent at higher voltages.

The other options provided do not align with the primary function of a transformer. Increasing current is not the purpose of a transformer; it primarily changes voltage levels. Measuring electrical resistance is done with devices like ohmmeters, and converting AC to DC is the role of rectifiers, not transformers. Understanding these distinct roles helps clarify the unique and vital function transformers serve in electrical systems.