Which term describes using two contacts of the same relay in series?

The term that describes using two contacts of the same relay in series is known as "reducing contact arcing." When two contacts are placed in series, they can effectively help manage the electrical load and minimize the arcing that occurs when contacts open and close. Arcing can cause wear and damage to the contacts, leading to decreased reliability over time. By utilizing two contacts in series, the circuit can share the current load, potentially reducing the amount of arcing at each individual contact, thereby extending the life of the relay and ensuring more reliable operation.

The other options do not relate directly to this specific arrangement of contacts. For example, a magnetic switch refers to a device that is operated by magnetic fields but does not imply the use of multiple contacts in series specifically for arcing reduction. Similarly, a walking beam is a component used in different mechanical systems and is unrelated to relay contacts, and a reed relay is a specific type of switching device that operates with reed contacts, which also doesn't denote the concept of using two contacts in series for arcing reduction.