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A wire connected to a bulb does not glow, whereas the filament of the bulb glows when the same current is passed through them. Why? |
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Answer» The wires are highly conducting are made up mainly of copper. The Filament is made up of Tungsten. Well, a material glows when an electric current is passed because it heats up. This heating is directly proportional to the resistance offered to the current. Since copper is a highly conducting metal (= Low resistance), it doesn't heat up to the point of melting of wire. But Tungsten offers more Resistance thus it heats up Glows. Also, Tungsten is chosen becaues it has the highest boiling point of all metals thus it won't melt away even when heated by an electric current. But there is danger of snapping of the wire and thus the bulb won't work if the thin tungsten wire has broken, then we say that the Bulb has Fused! |
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