What is the primary function of a step-down transformer?

The primary function of a step-down transformer is to lower the voltage and increase the current. This device works on the principle of electromagnetic induction and is designed to reduce the voltage from a higher level to a lower level while simultaneously increasing the current in proportion.

Transformers operate under the principle of energy conservation; thus, while the voltage is decreased, the current increases to maintain the same power level. For example, if a transformer steps down voltage from 240 volts to 120 volts, the current will increase accordingly to ensure that the overall electrical power remains constant (neglecting losses). This functionality is crucial in applications where lower voltages are needed for safety or compatibility with electrical devices.

In contrast to the other options, which include functions like increasing voltage, converting AC to DC, or enhancing signal strength, a step-down transformer specifically carries out the function of lowering voltage and increasing current, making option B the most accurate representation of its primary role.