Question

The wire of an electric lamp has a:
(A) High resistance and a high melting-point
(B) High resistance and low melting-point
(C) Low resistance and low melting-point
(D) Low resistance

Answer 1

When we consider using a material for an electric lamp, we need to know the physical properties of the material. The physical properties include boiling point, melting point, temperature, resistance, etc. The more is the resistance, more is the heating effect but the material should not reach its melting point.

Complete step by step solution:
Let us consider many physical properties like melting point, resistance of a material for using it as a wire of an electric lamp. For example, while Nichrome does have a much higher resistivity than Tungsten.
Tungsten has a much higher melting point than Nichrome (Nichrome has a MP = 1400 C, Tungsten has a MP = 3422 C). For a typical light bulb, the Tungsten filament operates at approximately 2500 Celsius.
We can say that this is actually above the melting point of Nichrome.
We know that tungsten is preferred over nichrome for filament wires. It is because we have to compare the operating temperatures of the light bulb to the melting point of the materials.
Thus, materials with high melting points are preferred mostly. Also, it should have high resistance compared to other materials.
Hence, the correct answer is option (A).

Note:
Tungsten has a very high melting point and thus is able to withstand heat and corrosion. Tungsten is one of the most durable types of filaments used in light bulbs. It must be exposed to very high temperatures before melting, and only the carbon arc has a higher heat resistance level than tungsten.