Fuse and the Earth Wire - Part II

Objectives

• Be able to calculate the current flowing in an appliance under normal operating conditions.

• Be able to select the correct fuse for an appliance, given information about its power rating or the current flowing.

Task 1 - Recap / Starter

Remind the person next to you:

• Which part of the appliance the earth wire is connected to.

• Whether the earth wire has a low or high resistance.

• How the fuse and earth wire work together to protect the user.

Task 2

Your teacher will show you how to use a "wattage and current meter" and how to select the correct fuse for an appliance.  Use the meter to complete the table with details of the power and current flowing through each of the the following appliances:

Select the correct fuse for each appliance, and fill in your choice in the final column of the table.

Task 3

When we cannot measure the current directly we can calculate it from the values of voltage and power, using the formula below:

Calculate the current flowing for the following devices, and hence select the correct fuse for each device:

Task 4

Your teacher will explain to you how to calculate the correct fuse for an appliance.  When you are happy you understand try these calculations, and select the correct fuse for each appliance in the table.