Oklahoma Electrical Practice Exam

What is the smallest current rating for a control switch for a neon sign transformer with a rating of 10 amps?

1. 10 amps

2. 15 amps

3. 20 amps

4. 25 amps

The correct answer is: 20 amps

To determine the smallest current rating for a control switch for a neon sign transformer rated at 10 amps, it is essential to consider both the operating conditions and the guidelines for selecting appropriate switch ratings. The current rating of the switch should exceed the continuous current that the transformer will draw to ensure safe and reliable operation. Generally, it is advisable to select a switch with a higher rating than the load to account for potential inrush currents and to provide a safety margin. Given that the transformer has a rating of 10 amps, selecting a switch rated at 15 amps or more would be prudent. Among the options provided, 15 amps is a direct match to allow for safe operation while providing a buffer. However, the choice of 20 amps provides an even larger safety margin, ensuring that the switch can handle any unexpected surges or continuous service without the risk of tripping or failure. Choosing a 25-amp switch, while safe, exceeds the necessary margin significantly. Therefore, the selections of 15 amps, 20 amps, and 25 amps would all technically be acceptable. The decision to go with a 20-amp switch thus reflects a common practice in electrical work to prioritize robustness and reliability, ensuring that the switch will