A fuse is a safety device that is added to an electrical circuit to prevent excessive current flow. It has the same function as a circuit breaker. However , a fuse must be replaced once it melts (blows). A circuit breaker can be reset after it trips.
Electric symbol for fuse
Fuse is connected to the live wire. It consists of a short piece of thin wire. In the event of an electrical fault, when a current that exceeds its fuse rating flows through, it heats up and melts (fuse blows). When the fuse blows, the electrical appliance is disconnected from the high potential of the live wire (usually 240 V). Hence it protects the appliance and the user.
The choice of fuse is always slightly higher than the actual current flowing through the appliance, and it has to be a whole number. Typical household fuses off the shelves are rated at 1 A, 2 A, 3 A, 5 A, 10 A and 13 A. But in theory, we just state a fuse which is slightly higher and is a whole number.
An electric cable contains three wires live, neutral and earth. The cable is correctly wired to a plug which contains a 3A fuse. The insulation becomes damaged and bare metal wires show.
Five possible events can occur.
How many of these five events cause the fuse in the plug to blow?
A 1 B 2 C 3 D 4
Solutions: Option B
Consider the five events: