Fuses
Applied Science: BTEC Level 3 National Extended Diploma, topic 3.7.7
Fuses and Circuit Breakers
Fuses and circuit breakers protect us from electrical appliances by stopping the flow of electric current flow if it gets too high. This stops the appliance overheating.
Fuses
- Fuses contain a thin wire that melts if the current flowing through an appliance is too high.
- This breaks the circuit and stops the flow of electric current.
Circuit breakers
- Circuit breakers are special devices that switch off the flow of current if the current is higher than a certain value.
- Circuit breakers do the same job as fuses but can be used lots of times.
Fuse Ratings and Circuit Breaker Settings
Fuses and Circuit Breakers must be chosen correctly to allow correct function.
Fuse ratings
- Fuse ratings tell us the level where a fuse will begin to melt. The fuse chosen should have a value just above the normal current that an electrical appliance uses.
- For example, if the operating current is 3.9 A, and fuses with values of 3 A, 5 A or 13 A are available, the most suitable fuse is the 5 A fuse.
Test yourself on Fuses
Which of these is not a property of circuit breakers?
What are the advantages of circuit breakers over fuses?
Why is a 13 A fuse wrong to use for an appliance with a 3.9 A operating current?
Which fuse should you use for an appliance with an operating current of 6.5A?
What do you need to know to select an appropriate fuse for a kettle?