Question

The rating of fuse wire is always expressed in

• A. Ampere hours
• B. Ampere volts
• C. Amperes
• D. Volts

Hint:

Always replace a blown fuse with one of the exact same Ampere rating. Using a fuse with a higher rating is dangerous as it might not blow when needed, leading to a fire.

Answer 1

The Correct Option is C

1. Fundamental Purpose: The primary job of a fuse is to melt and break the circuit when the current exceeds a specific limit. Since the melting of the fuse wire is caused by the heat ($I^2R$) generated by the

current, its rating must be based on that current.

2. Defining Ampere Rating: The "Ampere Rating" (e.g., 5A, 13A, 100A) represents the maximum continuous current the fuse can carry without melting. If a 5A fuse is subjected to 10A, the heat will quickly melt the element and open the circuit.

3. Why not other units?:

• Ampere-hours (Ah): This is a unit of charge, typically used for battery capacity.

• Volts: Fuses do have a maximum voltage rating (to prevent arcing after they blow), but their primary classification is always by current.

• Ampere-volts: This is equivalent to Watts (Power), which is not the standard way to rate a simple current-interrupting device.