Question

Why is Tungsten metal used in bulbs but not in fuse wires?

Answer 1

Hint: When attempting questions based on current and electricity like the one given to us above, keep in mind the different concepts regarding current, concepts surrounding how to increase or decrease current, how and what to do in case of short circuits et cetera.

Complete answer:
Fuse wires are basically a short piece of wire, made up of a material which has high resistivity and a low melting point so that it melts down when the current crosses the designated limit and the wire overheats due to the excess current flow. The thickness of the wire is determined based on the predetermined maximum current flow in the circuit. The main point of the fuse wire is to melt and break the circuit so that the appliances connected to the switch are not damaged due to the excess current flow.
Tungsten is a special metal alloy which is commonly used to make filaments of bulbs because of its unique property to glow when current is passed through it. Since it is an alloy it has a very high melting point and has a high resistivity so that it doesn’t burn easily under room temperature.
Tungsten metal cannot be used in fuse wires but is only used in bulbs because fuse wires have one purpose and that is to melt when current goes over the limit, but due to tungsten being an alloy it has a high melting point and resistivity, which makes it difficult to melt and hence it won’t serve the purpose of being a circuit breaker and can hence lead to damaging of the appliances connected to the system.
Hence we can say that due to the high melting point of Tungsten metal alloy, it cannot be used in fuse wires due to the requirements of fuse wires to have low melting point.

Note: Fuse wire cannot be used again once it has melted off and broken the connection of the system. Instead we can use other circuit breakers which can be used again and again because they only switch off the connection of the system with the click of a switch and to use them again we just need to switch it on again.