Zap Into Success: Electrify Your NCEA Level 3 Exam Skills 2026!

The primary function of a step-down transformer is to decrease voltage while increasing current. This operation is based on the principles of electromagnetic induction. In a step-down transformer, the turns ratio of the primary coil to the secondary coil is such that the number of turns in the secondary coil is less than that in the primary coil.

When alternating current passes through the primary coil, it creates a magnetic field that induces a voltage in the secondary coil. Because the secondary coil has fewer turns, the voltage output is lower than the input voltage. According to the law of conservation of energy (ideal transformers), while the voltage decreases, the current in the secondary coil increases to ensure that the power (voltage multiplied by current) remains relatively constant, assuming no energy losses.

This transformation is crucial in power distribution systems, where high voltages can be stepped down for use in homes and businesses, allowing safe and efficient delivery of electricity.

The other options do not accurately describe the function of a step-down transformer, as they either suggest an increase in voltage or maintaining constant values, which do not align with how step-down transformers operate.