Question

Give a reason why an alloy of lead and tin is used for making a fuse wire .

Answer 1

Hint :A fuse wire is made of a piece of metal or an alloy that is used as a safety measure in electrical circuits and devices. This is to prevent it from overloading or short circuiting. When the circuit gets heated up, the fuse wire melts and breaks the circuit thus preventing the electrical device from further damage.

Complete Step By Step Answer:
Fuse wire is a safety device that prevents the electrical device from short circuit. When an electrical overload occurs and the temperature suddenly increases, the fuse wire melts and the current flow is interrupted . Thus the device gets protected . It is usually made of a metal or an alloy. It must have a low melting point and high resistivity. Metals like aluminium, chromium, nickel, iron can be used. But an alloy of lead and tin is used more preferably due to the above mentioned reasons : low melting point and high resistance.
The heat produced will be , $ H = {I^2}R $ . When a large amount of current passes and due to high resistance, heat produced will be large . Due to the low melting point, it melts very quickly and breaks the circuit. Therefore, alloy of lead and tin is used to make a fuse wire.

Note :
Though metals and alloys are used, not all metals cannot be used to make a fuse wire. Melts with high melting point or low resistance should not be used. For example, copper cannot be used as a fuse wire due to its high melting point. It does not melt quickly thus harming the device. Copper wires have high electrical conductivity and therefore can be used as conducting wires.