🔍 Key Concepts

• Characteristics of a series DC motor (what happens to speed when load/torque changes) • Back EMF (electromotive force) and how it relates to armature current and speed • How centrifugal force on the rotor parts changes with RPM and what could cause overspeed

💭 Think About

• Think about how current and torque in a series DC motor depend on the load on the shaft. What happens to speed if the load suddenly becomes very small or zero? • Which of the listed operating conditions would most likely allow the motor to accelerate without effective limitation, increasing RPM to dangerous levels? • For each option, ask: does this condition tend to limit speed automatically, or could it allow speed to run away?

✅ Before You Answer

• Verify under which condition a series-wound motor develops very high speed because of reduced armature current and increased back EMF. • Check whether operating on AC affects speed mainly, or causes other issues such as heating, noise, or poor performance. • Confirm which situation is specifically warned about in marine electrical texts for series DC motors as a dangerous overspeed condition.