What happens to the voltage when using a step-down transformer?

When using a step-down transformer, the primary function is to reduce the voltage from the primary winding to the secondary winding. In a step-down transformer, the number of turns in the primary coil is greater than the number of turns in the secondary coil. This difference in the number of turns directly influences the transformation of voltage levels.

According to the transformer principle, the voltage ratio is proportional to the number of turns in the respective coils. As the transformer decreases the number of turns in the secondary relative to the primary, this results in a reduction of voltage across the secondary terminal. Therefore, when a step-down transformer is utilized, the voltage decreases, making the answer correct.

Other options do not align with how a step-down transformer operates. For instance, increasing voltage would occur in a step-up transformer, while voltage oscillating or remaining the same does not accurately describe the behavior of voltage transformation in this context.