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Rogue Physicist.  Free resources for physics education © 2006-2016 Dorian Pascoe.  Email: dorian.pascoe@hotmail.co.uk

Most resources are available under a Creative Commons Licence.  Visit our mirror at www.physicsweb.altervista.org

 

 

Mains Electricity

 

 

Objectives

• Be able to describe and explain the difference between DC and AC current.

• Be able to describe the colours and purpose of Live, Neutral and Earth wires.

• Understand why insulation is important for mains voltage.

 

 

 

 

Task 1 - Recap

Remind the person next to you:

• How the resistance of a bulb changes with temperature, and why this happens.

• How the resistance of a thermistor changes with temperature, and why this happens.

• How the resistance of an LDR changes with light intensity, and why this happens.

• The difference between DC and AC current.  You met these in our work on the national grid in year 10!

 

 

 

 

Task 2

Mains electricity uses AC current, and is slightly different to the DC current which flows in the circuits we have built so far.  Your teacher will explain the difference between AC and DC current using the simulation below.

Teacher note: there is a local copy stored here if the phet website is inaccessible.

 

 

 

 

Task 3

Write the title "Mains Electricity" in your exercise book.  Your teacher will give you a copy of the text below.

 

There are two types of electrical ____________. The first is DC, which stands for ____________ current. This is the type of current that flows from a battery or cell, and is most familiar to us. The direction of flow of the charges is always __________________.

 

The second type of current is AC, which stands for ________________ current. In this type of current the direction of flow of the charges is constantly _______________. UK mains electricity is AC, and it changes direction ______ times per second. We say that it has a ______________ of 50Hz.

 

Mains electricity is also a much higher _____________ than is produced by most cells or batteries. This can make it very dangerous. The cables have to be covered with plastic _____________ to prevent users being harmed.

 

Fill in the missing words and stick the sheet into your exercise book.  When you have finished, your teacher will check your answers.

 

 

 

 

Task 4

Another important difference with mains electricity is the high voltage (230V), which can present considerable danger to the user if there is a fault.  This necessitates a third wire in many appliances.  You need to know the colours of each wire in the plug, and where they are connected.  Your teacher will give you a plug, like the one below, to take apart.

 

 

Strip the plug down into the separate component parts, and then try to put it back together again.  When you have finished, show your teacher before putting the case back together.

 

SAFETY:

Your plug has a rivet through one of the pins to prevent you from plugging it in, but even so you MUST NOT attempt to plug your plug into a mains socket.

 

 

Your teacher will give you a diagram, like the one below, and some colouring pencils.  Show the colour of the insulation on each wire, and give each part of the plug a suitable label.

Teacher note: need to create link to digital copy of diagrams!

 

 

 

Task 5

Were you correct?  Find out, by helping your teacher to correctly label the parts of the plug on the diagram below.

 

 

 

 

 

Homework/Extension

Lots of different materials are used in the construction of a plug.  This sheet lists some of the materials which are commonly used, with the characteristics that makes them useful.  Match each material to the correct description and stick them into your exercise book.

 

Make sure your work is labelled "Gwaith Cartref" and has a date.