In a step-down transformer, the primary coil has more turns of wire than the secondary coil. When alternating current (AC) flows through the primary coil, it generates a magnetic field that induces a voltage in the secondary coil due to electromagnetic induction. The transformer operates based on the principle that the voltage ratio between the primary and secondary coils is directly proportional to the number of turns in each coil.
Since a step-down transformer is designed to reduce voltage, the number of turns in the secondary coil is less than that in the primary coil. As a result, the voltage in the secondary coil is lower than the voltage in the primary coil. This characteristic allows step-down transformers to provide lower voltages suitable for various applications, such as powering household appliances and other devices that require less voltage than what is available from the mains supply.
Thus, when using a step-down transformer, the voltage is indeed decreased, making the correct response that the voltage decreases when using this type of transformer.