What are the two primary designs for receptacle current contacts?

The primary designs for receptacle current contacts are best categorized as single-wipe and double-wipe configurations. Single-wipe contacts involve a contact that makes a single point of engagement, while double-wipe contacts have two points of engagement which help to improve the conductivity and reliability of the connection.

The single-wipe design is simpler and generally used in applications with lower current requirements, whereas the double-wipe design is favored in more demanding situations because of its superior ability to maintain a secure connection over time. By utilizing two contact points, double-wipe designs minimize the risk of oxidation and improve the durability of the electrical connection, particularly in environments where the connection may be repeatedly made and broken.

The other options reflect different characteristics or types of connections but do not specifically relate to the contact designs of receptacles in electrical engineering. For instance, the terms "direct" and "indirect," as well as "flexible" and "rigid," refer more to the physical attributes and configurations of wiring or connectors rather than the actual design of the contacts themselves. Thus, the terms pertaining to the primary designs of receptacle current contacts specifically highlight the operational performance and reliability, making the first answer the most relevant.