Torch (flashlight) and petri dish: what they have in common

1. Step 1. Torch (flashlight) — has part — Incandescent light bulb. A bulb (today an LED).
2. Step 2. Incandescent light bulb — works like — Heating element. A lamp and a heater use the same effect — a conductor heated by current; they differ in purpose, light or heat.
3. Step 3. Heating element — is part of — Electric kettle. A heating element in the base heats the water.
4. Step 4. Electric kettle — evolved from — Kettle. A kettle with a heater.
5. Step 5. Kettle — has part — Pot lid. A cap.
6. Step 6. Pot lid — is part of — Petri dish. A cap.

Open Evothings