Filaments

Question 1

What are the three types of automotive lightbulbs?

Answer 1

• halogen - tungsten filament
• LED
• xenon/high intensity discharge

Question 2

How are halogen lightbulbs used as trace evidence?

Answer 2

• has a tungsten filament
• tungsten is rigid and brittle at ambient temperatures and ductile at incandescent operating temperatures
• oxidised when exposed to atmosphere at operating temp - microscopic analysis
• glass can be fused to filament - SEM-EDX

Question 3

How can you tell if the filament of a halogen lightbulb was off?

Answer 3

• off: no pronounced distortion
• on: inertial force distortion on hot filament