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© Boardworks Ltd 2005 KS4 Electricity - Electromagnetism.

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Presentation on theme: "© Boardworks Ltd 2005 KS4 Electricity - Electromagnetism."— Presentation transcript:

1 © Boardworks Ltd 2005 KS4 Electricity - Electromagnetism

2 © Boardworks Ltd 2005 What is a magnetic field? Where would you find a magnetic field?

3 © Boardworks Ltd 2005 Around every magnet is an invisible force field that will affect all magnetic objects inside it. The magnetic field of a bar magnet is seen with iron filings. N S Magnetic field What does the magnetic field around a bar magnet look like? strongest field at poles Where is the magnetic field strongest?

4 © Boardworks Ltd 2005 What materials will stick to magnets? Look around the laboratory or your teacher will provide a tray. See which materials will stick to a magnet and which materials will not. Magnetic materials Non-magnetic materials

5 © Boardworks Ltd 2005 Magnets and materials N S What materials are magnets made from? Iron or steel. What materials will magnets stick to? Iron or steel. And nickel!

6 © Boardworks Ltd 2005 Forces between magnets – experiment

7 © Boardworks Ltd 2005 Repulsion and attraction Repel/attract Unlike poles attract. Like poles repel.

8 © Boardworks Ltd 2005 Separating coins N S How could you separate steel and gold coins using a magnet? Steel coins would stick to magnet, gold coins would be left behind.

9 © Boardworks Ltd 2005 What does the magnetic field for a bar magnet look like? In what direction do magnetic field lines point? N North to South S

10 © Boardworks Ltd 2005 Revising magnetism I Magnets are made from which materials? ___________ What are the ends of a magnet called? __________ What do we call the area around a magnet where a magnetic force exists? __________________ What does the word attract mean?__________ What does the word repel mean?__________ Iron or steel The Poles The Magnetic Field Pull together Push apart

11 © Boardworks Ltd 2005 What will two north poles do if brought together? _____ What will two south poles do if brought together? ______ What will a north and a south pole do if brought together? _______ What materials are attracted by magnets? ___________ Is magnetism a contact or non-contact force? _________ Repel Attract Iron and steel Non-contact Revising magnetism II

12 © Boardworks Ltd 2005 Electromagnets A coil of wire acts like a bar magnet when it has an electric current flowing through it. One end of the coil becomes a north-seeking pole. One end of the coil becomes a south seeking pole. This is called an electromagnet.

13 © Boardworks Ltd 2005 Making an electromagnet: Apparatus: Batteries Wire Iron Nail What to do: 1.Wrap a coil of wire around the iron nail. 2.Connect the coil of wire to the batteries. 3.See how many paperclips you can pick up.

14 © Boardworks Ltd 2005 Results How many paperclips could you pick up? Can you think of any ways to make the electromagnet pick up more paperclips? More batteries (more current) Number of paperclips Number of batteries More turns of wire on the coil Number of paperclips Number of turns

15 © Boardworks Ltd 2005 Electromagnetic strength – experiment

16 © Boardworks Ltd 2005 The results for the number of drawing pins attracted to the electromagnet with no core are: Electromagnetic strength - results number of cells number of coils How does changing the current affect the strength of an electromagnet? How does changing the number of coils affect the strength of an electromagnet?

17 © Boardworks Ltd 2005 Compare the results for the number of drawing pins attracted to the electromagnet with no core and an iron core: Electromagnetic strength - results number of cells number of coils number of cells number of coils What effect does an iron core have on the strength of an electromagnet?

18 © Boardworks Ltd 2005 Compare the results for the number of drawing pins attracted to the electromagnet with no core and a copper core: Electromagnetic strength - results number of cells number of coils number of cells number of coils What effect does a copper core have on the strength of an electromagnet?

19 © Boardworks Ltd 2005 Ways to make an electromagnet stronger There are three ways to make an electromagnet stronger. Do you know them? 1.___________________ 2.___________________ 3.___________________ More turns on the coil More electrical current Using an iron core S N What happens if you turn the battery around in an electromagnet? S The poles on the coil reverse, north becomes south and south becomes north.

20 © Boardworks Ltd 2005 What do like poles do? A.Attract and repel B.Attract C.Repel D.Stick together

21 © Boardworks Ltd 2005 Which material below will not stick to a magnet? A.Steel paper clip B.Aluminium can C.Iron nail D.Steel key

22 © Boardworks Ltd 2005 Which of the below will not increase the strength of an electromagnet? A.More coils B.More current C.Less current D.Iron core

23 © Boardworks Ltd 2005 In which direction do magnetic field lines always point? A.East to west B.West to east C.South to north D.North to south

24 © Boardworks Ltd 2005 Which of the following is not a use of electromagnets? A.Fridge magnets B.Loud speakers C.Relays D.Circuit breakers


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