Transistor radio and davy lamp: what they have in common

1. Step 1. Transistor radio — has part — Dry cell. Batteries.
2. Step 2. Dry cell — is part of — Torch (flashlight). Batteries.
3. Step 3. Torch (flashlight) — has part — Incandescent light bulb. A bulb (today an LED).
4. Step 4. Incandescent light bulb — evolved from — Oil lamp. The electric lamp replaced oil and gas lamps.
5. Step 5. Oil lamp — has part — Wick. The wick feeds oil to the flame.
6. Step 6. Wick — is part of — Davy lamp. A wick.

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