Unit 8: Electrical operations
LO1: Understand operating and performance
characteristics of electrical and electronic
components and devices
Selecting cables and fuses – fuses
Learner activity sheet
Activity 1
Fuses are devices that provide overcurrent protection in electric circuits. This includes protection against
damage to the circuit itself or fire in the event of an overload and protection to the user in terms of
receiving an electric shock.
Choosing the correct voltage rating, current rating and type of fuse for a particular application is crucial.
The diagram above shows a rectangular plate ABCD, with sides AB/CD of 2m, and AD/BC of 1m. It is
held in equilibrium by three forces, as shown in the diagram. If the mass of the plate is 50kg find the
values of F, P and Ɵ.
Begin this activity by considering the table below which shows some typical domestic appliances.
Assuming that the supply voltage is 240 V AC, determine the current rating of fuse that would be
selected for each application. You will need to research the range of standard current ratings for fuses
used in domestic applications. Justify your selections.
Version 1
Application
Fuse Current Rating
240 W radio
400 W plasma TV
1000 W hairdryer
1600 W electric kettle
3000 W electric oven
Activity 2
Apart from selecting fuses according to their current rating, the correct type of fuse must be selected for
the particular application. The table below shows common types of fuse. Investigate the characteristics
and applications of each fuse type – and complete the table.
Fuse Type
Characteristics
Applications
Slow-Blow/Time
delay/Anti-Surge
Quick/Fast Acting
Normal
High Rupturing
Capacity (HRC)
You may wish to analyse data sheets for actual fuses as part of this Activity, comparing the
characteristics of different fuse types.
Version 1