What is the main purpose of a transformer in electrical circuits?

Transformers play a crucial role in electrical circuits by modifying voltage levels for efficient power transmission and distribution. Their primary function is to either step up (increase) or step down (decrease) voltage levels based on the needs of the electrical system. This is essential because it allows electricity to be transmitted over long distances with minimal loss. By increasing voltage for transmission, current is reduced, resulting in lower energy losses due to resistance in the conductors. Conversely, at the point of use (like in homes or businesses), the voltage can be decreased to safer levels that are suitable for appliances and equipment.

The other choices do not align with the primary function of transformers. For example, while converting AC to DC is a different process that typically involves rectification, storing electrical energy is handled by capacitors or batteries, and measuring electrical consumption is done through metering devices. Hence, the correct answer highlights the fundamental purpose of transformers in adjusting voltage levels within electrical systems.