Journeyman Electrician Practice Exam

What condition must be met for motor control circuits to be disconnected from all sources of supply?

1. When the circuit is damaged

2. When the disconnecting means is in the open position

3. When the maintenance personnel are present

4. When the motor is locked out

The correct answer is: When the disconnecting means is in the open position

The requirement for motor control circuits to be disconnected from all sources of supply is met when the disconnecting means is in the open position. This action ensures that there is no electrical energy delivered to the motor or its control circuits, effectively making it safe for maintenance or inspection. When the disconnecting means is open, it signifies that the supply circuit is completely interrupted, preventing any possibility of accidental energization. This is a fundamental safety measure in electrical work, as it protects technicians and maintenance personnel from electric shock while performing their tasks on the motor or associated controls. Other conditions, such as the circuit being damaged or personnel presence, do not inherently guarantee that the entire circuit is de-energized. Locking out a motor is an important safety protocol, but it specifically applies to ensuring that the motor cannot be turned on without removing the lockout, which is often accompanied by properly opening the disconnect switch. Thus, the open position of the disconnecting means is the definitive condition that isolates the motor control circuit from the electrical supply.