Final answer:
A transformer uses alternating current as input and delivers alternating current with a modified voltage as output. It works on the principle of transforming voltages and conserves power under ideal conditions.
Step-by-step explanation:
A transformer is a device that transforms voltages from one value to another, contrary to one of the misinformation statements, it does not transform current to voltage or resistance of wire to voltage. It uses alternating current as an input and modifies the voltage level while conserving power (assuming ideal conditions). The output can then be an alternating current with either a higher or lower voltage depending on the type of transformer (step-up or step-down).
In the case of an American traveler's transformer which converts 240V to 120V for use in New Zealand, the ratio of turns in the primary to the secondary coil would be a factor of 2:1 to step down the voltage by half. If the input current is known, the output current can be calculated using the conservation of power in an ideal transformer, where the power input (voltage times current) on the primary side equals the power output on the secondary side.