What is the melting point of tungsten? If it is very high then why the filament of the bulb is covered with glass to protect it from melting or burning?

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Solution

Melting point of tungsten = $3, 422^{\circ} C$
In order to make tungsten filament glow, it is made very thin so that its resistance becomes very high causing emission of a lot of energy and the temperature of filament rises to a very high temperature and it starts glowing. At such a temperature, tungsten is prone to oxidation and so it is covered with glass or quartz bulb to prevent oxidation.
Then why not the coil of heater is covered as it also becomes enough hot to warm a room, don't it may get fire
Two facts should be considered here:
1)The temperature of the element in bulb is higher ( $2500^{\circ} C$ ) as compared to heating element of a toaster or a heater (usually $1500^{\circ} C$ )
2)The heating element is made from nichrome while bulb filament is tungsten (both having different susceptibility to oxidation)

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Similar questions

Why the filament of bulb has high melting point?

Q. Consider the following sentences.

1

. In ordinary bulbs only

5 %

10 %

electrical energy is converted into light energy.

2

. Tungsten has very high melting point as

3422^{o}

C, the filament of bulb is made of it.

3

. Mica has good electrical resistance.

4

. The electric bulb was first invented by Thomas Alva Edison.
Which of the statements are correct?

State true or false.
Tungsten is used almost exclusively for filament of incandescent lamps because tungsten has a high melting point ( $3380^{\circ}$ C) and becomes incandescent (i.e., emits light at a high temperature) at $2400 K$ .

Tungsten is used almost exclusively for filament of incandescent lamps because tungsten has a high melting point ( $3380^{\circ}$ C) and becomes incandescent (i.e., emits light at a high temperature) at 2400 K.

Q. The melting point of filament of a bulb is

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