Transistor radio and needle: what they have in common

1. Step 1. Transistor radio — has part — Dry cell. Batteries.
2. Step 2. Dry cell — uses — Electrochemical reaction. A chemical source of current.
3. Step 3. Electrochemical reaction — is used in — pH meter. A glass electrode.
4. Step 4. pH meter — is made of — Silver. The internal electrode is silver chloride.
5. Step 5. Silver — is material for — Syringe. Early needles were silver.
6. Step 6. Syringe — has part — Needle. A hollow needle.

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