🔍 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