What is the main characteristic of a transformer in an electrical circuit?

The main characteristic of a transformer in an electrical circuit is its ability to step voltage up or down. Transformers operate on the principle of electromagnetic induction, allowing them to change the voltage level while maintaining the frequency of the alternating current.

When alternating current flows through the primary coil of a transformer, it creates a magnetic field that induces a current in the secondary coil. Depending on the number of turns in the primary and secondary windings, the transformer can increase (step up) or decrease (step down) the voltage. This capability is crucial in electrical power distribution, as it allows for efficient transmission of electricity over long distances by stepping up the voltage before it travels along power lines and stepping it down for use in homes and businesses.

The other options do not accurately describe the primary function of a transformer. For instance, converting direct current to alternating current is the function of a device known as an inverter, not a transformer. Storing electrical energy is a characteristic of capacitors or inductors rather than transformers. Lastly, filtering radio frequency signals is typically associated with filters or tuned circuits designed for specific frequency responses, rather than the voltage transformation function of a transformer.