This question is about the physical properties and electrical applications of metals and alloys.
Table 1 shows information about three metals: aluminium, silver, and platinum.
| Metal | Electrical conductivity (arbitrary units) | Density in g/cm3\text{g/cm}^3g/cm3 | Approximate cost per kg (£££) |
|---|---|---|---|
| Aluminium | 38 | 2.7 | 2.10 |
| Silver | 63 | 10.5 | 650.00 |
| Platinum | 9 | 21.5 | 28,000.00 |
a.[4]
Evaluate the suitability of aluminium, silver, and platinum for the three applications shown in the diagram:
- Overhead transmission lines (Panel 1)
- High-fidelity audio cables (Panel 2)
- Cardiac pacemaker electrodes (Panel 3) (where corrosion inside the human body must be entirely prevented and only microscopic amounts of metal are used)
Use the information in Table 1 to support your evaluation.
b.[3]
Explain how metals conduct electricity. Refer to structure and bonding in your answer.
c.[2]
Pure silver is highly conductive. Sterling silver is an alloy made of 92.5% silver and 7.5% copper. Suggest why sterling silver has a lower electrical conductivity than pure silver. Answer in terms of structure and bonding.