Question

Explain the suitability of copper as an electrical conductor with reference to its mechanical
and electrical properties.

Answer 1

Introduction

Copper is the industry standard for electrical wiring and conductors, and its widespread use is due to an exceptional combination of both electrical and mechanical properties. While its electrical performance is paramount, its mechanical characteristics are what make it a practical, reliable, and durable material for a vast range of applications.

1. Electrical Properties

These properties relate to how well copper carries an electric current.

a) High Electrical Conductivity (Low Resistivity)

• Property: Copper has the second-highest electrical conductivity of any pure metal at room temperature, surpassed only by silver. Its resistivity is extremely low (approximately $1.68 \times 10^{-8}$ Ω·m).
• Suitability:
  • High Efficiency: Low resistance means that very little electrical energy is lost as heat when current flows through it ($P_{loss} = I^2R$). This makes power transmission highly efficient, which is critical for everything from national power grids to the circuitry inside a smartphone.
  • Higher Current Capacity: Because it generates less waste heat, a copper wire of a given size can safely carry more current than a less conductive material of the same size, such as aluminum. This allows for more compact and space-saving designs in motors, transformers, and electronic devices.

b) Predictable Temperature Coefficient of Resistance

• Property: Like most metals, copper has a positive temperature coefficient of resistance, meaning its resistance increases as its temperature rises. This relationship is well-documented and predictable.
• Suitability: While an increase in resistance is not ideal, its predictability allows engineers to account for it in system design. For high-power applications where conductors will heat up, the final operating resistance can be calculated to ensure the system performs safely and as expected.

2. Mechanical Properties

These properties relate to how copper behaves physically, which is crucial for its manufacturing, installation, and long-term reliability.

a) High Ductility and Malleability

• Property:
  • Ductility: The ability to be stretched or drawn into a thin wire without breaking.
  • Malleability: The ability to be hammered or rolled into thin sheets.
• Suitability: Copper's excellent ductility is fundamental to its use as a conductor. It can be easily and economically drawn into wires of various diameters, from thick power cables down to the hair-thin wires used for windings in motors and electromagnets. This makes manufacturing efficient and versatile.

b) Good Tensile Strength

• Property: Copper has high tensile strength, meaning it can withstand significant pulling forces (tension) before it deforms or breaks.
• Suitability: This strength is essential during installation. Wires need to be pulled through conduits, walls, and strung across supports without snapping. Its inherent strength ensures the conductor remains intact during the physical stresses of installation and throughout its service life, preventing breakages and failures.

c) Corrosion Resistance

• Property: Copper is a relatively noble metal, meaning it is resistant to oxidation and corrosion in most environments. When it does oxidize, it forms a thin, durable, and non-flaking layer of greenish-brown patina (copper oxide or copper carbonate).
• Suitability:
  • Longevity: This resistance to degradation ensures a very long service life for electrical installations, reducing maintenance and replacement costs.
  • Reliable Connections: Crucially, the patina does not significantly increase contact resistance at terminals and joints. This is a major advantage over a material like aluminum, which forms a hard, insulating oxide layer that can lead to overheating and connection failure if not properly managed.

d) Excellent Solderability and Joinability

• Property: Copper surfaces can be easily and effectively joined using soldering, brazing, or mechanical connectors (like crimping).
• Suitability: This makes it simple to create reliable, low-resistance, and permanent electrical connections. The ability to easily solder copper is essential for assembling printed circuit boards (PCBs) and creating secure wiring harnesses, ensuring the integrity of complex electrical systems.

Summary

It is the synergy of these properties that makes copper an almost ideal electrical conductor.

| Property Category | Key Property | Why it's Suitable for a Conductor |
| :--- | :--- | :--- |
| Electrical | High Conductivity | Minimises energy loss, allows for smaller wires, high efficiency. |
| Mechanical | High Ductility | Easy and cheap to manufacture into wires of any size. |
| Mechanical | Good Tensile Strength | Durable and resistant to breaking during installation and use. |
| Mechanical | Corrosion Resistance | Ensures long life and reliable, low-resistance connections. |
| Mechanical | Excellent Joinability | Allows for simple, secure, and permanent electrical connections. |

In conclusion, while its high conductivity is the primary reason for choosing copper, its robust mechanical properties ensure that it can be practically manufactured, installed, and relied upon for decades, making it the superior choice for the vast majority of electrical applications.