UV/LED nail lamp and voltaic pile: what they have in common

1. Step 1. UV/LED nail lamp — has part — LED. Modern lamps get their light from ultraviolet LEDs: the same semiconductor diodes as in a traffic light, just at a different wavelength.
2. Step 2. LED — is part of — Torch (flashlight). Modern torches use LEDs.
3. Step 3. Torch (flashlight) — has part — Dry cell. Batteries.
4. Step 4. Dry cell — evolved from — Voltaic pile. A convenient form of the galvanic cell.

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