Aluminium is widely used as a material for bus-bars, which are conductors used to carry substantial electric current from one part of an electrical system to another. When selecting a material for bus-bars, several factors are considered, including conductivity, cost, weight, availability, and ease of fabrication.

Why Aluminium is Preferred for Bus-bars

Let's examine the given options and compare aluminium to other common conductor materials like copper.

• Its low cost: Aluminium is significantly less expensive than copper for the same volume or weight. Although copper has higher electrical conductivity than aluminium per unit volume, aluminium has better conductivity per unit weight. For large current applications like bus-bars, the total cost is a major consideration. Using aluminium allows for a larger cross-sectional area to achieve the required conductivity at a lower overall material cost compared to using copper. This cost-effectiveness is a primary reason for its widespread use.
• Its low density: Aluminium has a density of approximately \(2.7 \, \text{g/cm}^3\), while copper has a density of around \(8.9 \, \text{g/cm}^3\). This means aluminium is much lighter than copper. The low density is advantageous, especially in applications like overhead transmission lines or large bus-bar installations where weight can impact structural requirements and installation costs. While important, cost is often the dominant factor driving the preference for aluminium in many bus-bar applications.
• Non-availability of copper: Copper is a widely available metal, so its non-availability is generally not a reason to prefer aluminium. Both metals are readily available on the market, although market price fluctuations occur.
• The ease of fabrication: Aluminium can be easily fabricated into various shapes and sizes required for bus-bars. It is ductile and malleable. Copper is also relatively easy to fabricate. While ease of fabrication is a factor, it is often comparable between the two metals and not the primary reason aluminium is preferred over copper in many cases.

Comparing the factors, while aluminium's low density and ease of fabrication are beneficial properties, the most significant advantage that leads to aluminium being preferred over copper for bus-bars in many applications, especially large-scale ones, is its significantly lower cost.

Therefore, the low cost of aluminium makes it an economically attractive material for bus-bar installations, allowing for large currents to be conducted efficiently without incurring the higher material expenses associated with copper.