What is the functional purpose component "5" as shown in figure "B" of the illustration? Illustration EL-0081

Correct Answer: Option D — initially heat the fluorescent tube filaments at startup and cause the ballast to strike the arc to fire the tube after warm-up

The thermal starter switch (component 5) utilizes a bimetallic strip to initially close the circuit, preheating the cathode filaments to emit electrons, then opening to create a voltage transient across the ballast that ignites the main arc.