Oilers/Plant Tenders (HHC) Civil Service Practice Exam

Regarding torque-equipped machines, which statement is MOST NEARLY CORRECT?

1. They have minimal power output at stall conditions

2. At stall conditions, the engine is putting out its maximum power

3. Torque decreases significantly at high RPM

4. They do not function under heavy load

The correct answer is: At stall conditions, the engine is putting out its maximum power

The assertion that at stall conditions, the engine is putting out its maximum power is rooted in the relationship between torque and power in engines. In this context, stall conditions refer to a state where the machine is not moving despite the engine being actively engaged. At stall, the engine's torque is indeed at its peak. However, it’s essential to clarify that while torque is maximum, power output at that moment is not; power is calculated as the product of torque and angular velocity. Since the RPM (revolutions per minute) is zero at a stall, the power output remains zero despite the engine's high torque. This understanding highlights the nature of stall conditions in torque-equipped machines. Therefore, under normal operational conditions outside of a stall, high torque ensures efficient power delivery, which can be misleading if one focuses solely on stall conditions without considering the RPM factor. This statement about stall conditions can create confusion, as it's easy to mistakenly equate high torque directly with high power, regardless of the engine's speed.