Question

What should be the characteristic of fuse wire?
A. High melting point, high specific resistance
B. Low melting point, low specific resistance
C. High melting point, low specific resistance
D. Low melting point, high specific resistance

Answer 1

We know that a fuse is a safety instrument which consists of a wire that melts and breaks to stop the current flowing in an electric circuit when current increases than its safe value. Thus, the main function of a fuse is to prevent any damage of an appliance if current exceeds the safe value. Keeping this in mind, the characteristics of fuse wire are decided.

Complete answer:
The characteristics of any device depend on its function. In case of fuse wire, its main function is not to
allow a current higher than a certain safe value to avoid any damage. When the current in the circuit
starts increasing from its normal rated value, the fuse wire starts heating which rises its temperature.
Now, to protect the device from the damage the wire must melt to break the circuit. This is possible
when the wire can melt easily which means it should have low melting point. If the wire has high melting
point, it takes time to break the circuit which may damage the appliance.

We know that fuse wire is connected in series with the circuit to limit the amount of current flowing
through the circuit. Now, if the wire has low specific resistance or resistivity, it may allow large amount
of current to pass through the circuit which may damage the circuit and the device. On the other hand,
fuse wire with high specific resistance does not allow large amounts of current to go through the circuit
which protects the devices connected in series with the fuse wire. Thus, the fuse wire should have low melting point and high specific resistance.

Hence, option ‘D’ is the correct answer

Note: A fuse wire is designed by taking some considerations. For example, its fusing action should be predictable, its operation should be safe without creating any harm to the appliances and its body and the supporting structure should not catch the fire. If the combustion takes place, then there will be a risk of setting the house or a factory on fire which should be taken care of at the designing process only.