Question

# Which is or are the correct for filament of bulb?A. Low melting pointB. High melting pointC. Made of tungstenD. Made of nichrome

The metal tungsten has the resistivity of $4.8 \times {10^{ - 8}}\;\Omega m$ and the melting point is $3422{\;^ \circ }C$. Hence, it is the suitable material for filament of bulb.
Note: The tungsten filament lamp temperature is about $2800 - 3300\;K$ and consists of a linear double-ended quartz tube containing a tungsten filament, which is resistively heated. The quartz tube heats up to $400{\;^ \circ }C$ or more and the upper permissible temperature limit is $900{\;^ \circ }C$. Halogen gas is used instead of inert gas because it increases the filament colour temperature by about $300\;K$. Also, it prevents tungsten deposition on the quartz wall, due to a regenerative tungsten halide chemical transport cycle above $250{\;^ \circ }C$ quartz wall temperature.