Why Copper Wire Cannot Be Used as a Fuse Wire?

Question:

State two reasons why a copper wire cannot be used as a fuse wire.

Answer:

Copper wire cannot be used as a fuse wire because of Low Resistance and Inadequate Melting Point.

Explanation:

Copper's Low Resistance: Copper wires possess excellent electrical conductivity, but their use as fuse wires is hindered by their low resistance. When a high current flows through a wire due to a short circuit or excessive load, the wire heats up. A fuse wire needs to melt promptly to interrupt the current and prevent equipment damage or fire. Copper's low resistance directly affects its ability to generate heat. A lower resistance leads to less voltage drop across the wire, causing the wire to heat up at a slower rate and delaying the melting process. This delay in melting time could allow damaging levels of current to persist.

Inadequate Melting Point: Copper's melting point is around 1,984°F (1,085°C), which is relatively high. Materials with lower melting points such as tin, lead, or alloys are preferred for fuse wires as they can melt rapidly under overcurrent conditions. A copper wire's delayed melting time due to its high melting point could lead to significant damage before the wire fuses. As a fuse's primary purpose is to act quickly to safeguard the circuit, materials with adequate melting points are essential to ensuring prompt interruption of the current.

Materials like tin, lead, or alloys with lower melting points are chosen for fuse wires because they can provide the rapid response required for circuit protection. These materials play a crucial role in ensuring that the circuit is interrupted promptly in case of overcurrent conditions, preventing extensive damage to equipment and property.