Final answer:
In a transformer, the primary winding has a lower voltage and higher current in a step-up transformer, while it has a higher voltage and lower current in a step-down transformer. To differentiate, there are usually electrical characteristics and labels indicating their function.
Step-by-step explanation:
To distinguish the primary winding from the secondary winding in a transformer, we can consider their voltage and current characteristics. A step-up transformer increases voltage from primary to secondary, so the primary voltage is lower, and the secondary voltage is higher. Conversely, in a step-down transformer, the primary voltage is higher than the secondary voltage. The current, on the other hand, is inversely proportional due to the conservation of power (assuming ideal conditions without losses); therefore, the primary current would be higher than the secondary current in a step-up transformer and lower in a step-down transformer.
In dual voltage systems, the auxiliary windings are reversed to change the magnetic field direction, ensuring the proper operation of the device with different voltage levels. Also note that in parallel circuits, currents and power are greater compared to series circuits, signifying that in a transformer, different configurations can affect the overall performance and characteristics.