If the secondary voltage is smaller than the primary voltage in a transformer, what type of transformer is it?

In a transformer, the relationship between primary and secondary voltage is defined by the turns ratio of the windings. If the secondary voltage is smaller than the primary voltage, this indicates that the transformer is designed to decrease voltage levels. This type of transformer is known as a step down transformer.

Step down transformers are commonly used in applications where it is necessary to reduce high voltage levels to lower voltages suitable for consumer use, such as in the distribution of electricity from substations to homes. The design allows the primary winding to have more turns of wire than the secondary winding, which results in a lower voltage output on the secondary side compared to the input on the primary side.

In contrast, a step up transformer increases voltage, an isolation transformer serves to transfer electric power while providing electrical isolation between circuits, and an auto transformer is a single winding transformer with a portion of the winding common to both primary and secondary circuits. None of these options would correctly apply when the secondary voltage is smaller than the primary voltage.