New York State Master Electrician Practice Exam

What is the consequences of using a knife switch under load when it is rated for isolating purposes only?

1. It will operate correctly but inefficiently

2. It could cause an electrical fault

3. It will not function at all

4. It could result in overheating

The correct answer is: It could cause an electrical fault

Using a knife switch that is rated for isolating purposes only under load can create significant safety hazards. Such switches are designed to disconnect power safely when no load is present, and when operated under load, the risk of creating an electrical fault increases. This condition may result in an arc as the contacts of the switch separate while current is flowing, which can lead to damage to the switch itself and pose a fire risk. When a knife switch is engaged while under load, it can also result in equipment damage, exacerbate wear on the switch, and potentially endanger operators. Therefore, the consequence of using a knife switch inappropriately in this manner is that it could cause an electrical fault, making it crucial to use switches according to their ratings and intended applications for safety and reliability.