What is a transformer used for in electrical systems?

A transformer is a crucial component in electrical systems due to its primary function of adjusting voltage levels in alternating current (AC) systems. It operates on the principle of electromagnetic induction, which allows it to either increase (step-up) or decrease (step-down) the voltage. For example, in power distribution, transformers raise the voltage for efficient long-distance transmission and then lower it to safer levels for consumer use. This versatility makes transformers invaluable in ensuring that electrical energy can be transported over vast distances while minimizing losses, and adapting to the voltage requirements of different devices and systems.

The other options refer to other electrical components but do not accurately describe the purpose of a transformer. Storing electric energy is the role of capacitors or batteries, converting AC to DC is performed by rectifiers, and measuring electrical resistance is done with ohmmeters. Each of these serves distinct functions within electrical systems.