How does contact wear differ between DC switches and AC switches?

• A. Less on DC switches
• B. Greater on DC switches
• C. Equal on both
• D. Greater on AC switches

Answer: (B)

Contact wear refers to the degradation of the electrical contacts within switches, which can significantly impact their performance and longevity. In the case of DC switches, the current is unidirectional, meaning that the electrical arc generated during contact opening tends to be more focused and persistent. The lack of zero-crossing in direct current makes it more challenging to extinguish the arc when contacts separate, resulting in higher wear on the contacts.

Conversely, AC switches experience a current that alternates direction, which provides natural opportunities for the arc to extinguish as the current crosses zero. This reduces the overall energy of the arc compared to that seen in DC switches. Because of this mechanism, DC switches generally experience greater wear on their contacts than AC switches do.

Understanding the differences in contact wear is crucial for selecting the right type of switch for specific applications, especially in environments where frequent switching is required. This knowledge helps in maintaining equipment reliability and longevity.