Which of the following materials is not used for transmission and distribution of electrical power ?
A
Tungsten
B
Copper
C
Steel
D
Aluminium

Question

Which of the following materials is not used for transmission and distribution of electrical power ?

Examoogle · Accepted Answer

Tungsten

Explanation: Tungsten is not used for transmission and distribution of electrical power because it has an extremely high resistivity compared to common conductor materials like copper or aluminium. While it possesses a very high melting point, its high electrical resistance leads to excessive energy loss in the form of heat during power transmission, making it inefficient for long-distance utility applications.

Working Principle: The efficiency of a power transmission line is inversely proportional to its resistance ($R = ho \frac{L}{A}$). Materials like Copper and Aluminium are chosen for their low electrical resistivity ($ho$), ensuring minimal $I^2R$ power losses and voltage drops across long distances. Tungsten's high resistivity and brittleness make it unsuitable for overhead conductors, where flexibility and high conductivity are mandatory requirements.

Key Formulas: $R = ho \frac{L}{A}$ — Resistance of a conductor; $P_{loss} = I^2R$ — Power loss in transmission lines

Key Points: Copper has high conductivity and ductility, making it ideal for low-voltage distribution.; Aluminium is cheaper and lighter, standard for high-voltage transmission lines (ACSR).; Steel provides mechanical strength, often used as a core in ACSR conductors.; Tungsten is primarily used for incandescent filaments due to its high melting point and resistance.

Advantages: Copper: Excellent conductivity, high corrosion resistance.; Aluminium: Lightweight, cost-effective for long spans.

Disadvantages: Tungsten: Extremely high resistivity leading to massive power losses.; Tungsten: Brittle nature makes it prone to snapping under wind or tension.

Applications: Copper: Indoor wiring, underground cables.; Aluminium: Overhead transmission lines, utility distribution networks.

Additional Info: Resistivity of Copper $\approx 1.72 	imes 10^{-8} \Omega\cdot m$.. Resistivity of Tungsten $\approx 5.6 	imes 10^{-8} \Omega\cdot m$ at room temperature, increasing significantly with temperature.

Answer: A is correct — Tungsten is unsuitable for power transmission due to its high resistivity and brittle mechanical properties.

Exam Tip: Always remember the 'L-C-A' rule for power lines: Light weight (Aluminium), Conductivity (Copper), and Added Strength (Steel core).

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