🔍 Key Concepts
• Difference between incandescent lamps and discharge lamps (like sodium or mercury vapor)
• Role of a filament in producing light vs. an arc discharge tube with electrodes and ballast
• How an incandescent lamp connects directly to the supply without needing a ballast or igniter
💭 Think About
• Look at each figure in the illustration and decide which one shows light being produced by a heated wire rather than by an electrical discharge through gas or vapor
• Compare which circuits include extra components such as a choke coil, transformer, ballast, or igniter, and which one could run directly from the supply
• Focus on the construction labels: which lamp mentions a filament, and which ones describe discharge tubes, sodium retention, or mercury vapor?
✅ Before You Answer
• Identify the figure that clearly shows a wire filament as the main light‑producing element
• Confirm that the same figure does not require a ballast, transformer, or igniter in its circuit to operate
• Verify that the other figures use terms like discharge tube, sodium, mercury vapor, or ballast, which indicate gas‑discharge (not incandescent) lamps