*Question T0A03:
In the United States, what circuit does black wire insulation indicate in a three-wire 120 V cable?*  

*Correct Answer is  B: Hot*  

### AI Response: (may contain errors)  

In the United States, the black wire insulation in a three-wire 120 V cable indicates a "Hot" circuit. Here's a breakdown of why this is the correct answer and why the other options are incorrect:

1. **Correct Answer: Hot**
   - The National Electrical Code (NEC) designates black insulation for hot wires. A hot wire carries the electrical current from the power source to the load (like a light or appliance). It is important to identify hot wires correctly for safety and proper circuit function.

2. **Why the Other Choices are Incorrect:**
   - **A: Neutral**
     - Neutral wires are typically insulated in white or gray. They provide a return path for current and are grounded at the main electrical panel.
   - **C: Equipment ground**
     - Equipment ground wires are usually bare or insulated in green. They are used for safety to prevent electrical shock by providing a path for fault current.
   - **D: Black insulation is never used**
     - This statement is false because black insulation is commonly used for hot wires in residential and commercial wiring.

3. **Useful Rules of Thumb:**
   - In a standard 120 V circuit:
     - **Black**: Hot
     - **White**: Neutral
     - **Green or Bare**: Ground

Understanding these color codes is crucial for safe electrical work and compliance with electrical codes.